JP2003227759A - Optical sampling waveform measuring device and polarization separator - Google Patents

Abstract

(57) [Problem] To accurately measure a pulse waveform of a measured light even if the polarization state of the measured light changes. A sampling light source 10 for generating a pulse train of the sampling light b ₁ having a narrow single plane of polarization of the pulse width from A measured light a, the polarization plane is different by 90 degrees outputted the sampling light and the measured light from each other A polarization demultiplexer 11 that separates the sampling light and the light to be measured into two lights, and separates the sampling light and the light to be measured, which are separated by 90 degrees from each other, and outputs the combined lights to different optical paths; A pair of non-linear optical materials 1a and 1b for generating, as sum frequency light, a cross-correlation signal of the sampled light and the light to be measured whose polarization planes differ from each other by 90 degrees, and a pair of materials for converting the output sum frequency light to an electric signal. And a signal processing unit 12 for adding the output electric signals, processing the added electric signals, and displaying a pulse waveform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical sampling waveform measuring device for measuring a pulse waveform of an optical signal used in optical communication or the like by using a sum frequency light, and a polarization splitting device which can be incorporated in the measuring device. Regarding vessels.

[0002]

2. Description of the Related Art When a new optical communication system is constructed, a new optical transmission device is manufactured, or when these are periodically inspected in order to grasp the quality of optical communication, digital signals transmitted and received are used. It is important to measure the pulse waveform of an optical signal.

As a conventional method for measuring the pulse waveform of this optical signal, an optical signal containing the pulse waveform is converted into an electric signal using, for example, a photoelectric converter, and the pulse waveform converted into this electric signal is converted into an oscilloscope. The output was displayed on the display screen.

However, in recent years, the transmission speed of information in optical signals has increased, and high-speed optical transmission of 10 Gbit / s or more is planned. However, with a high-speed optical signal exceeding several tens of Gbit / s, the response speed of a photoelectric converter that converts the optical signal into an electric signal cannot follow.

In order to eliminate such inconvenience, an optical sampling waveform measuring device for measuring the pulse waveform of an optical signal by using the sum frequency light has been developed (Japanese Patent Publication No. 6-63).
869).

FIG. 15 and FIG. 16 are views for explaining the measuring principle of this optical sampling waveform measuring device. For example, the light to be measured a having a repetition frequency f of the pulse waveform to be measured, a pulse width that is significantly narrower than the pulse width of the light to be measured a, and is slightly lower than the repetition frequency f of the light to be measured a (or When the sampling light b having a (high) repetition frequency (f−Δf) is simultaneously incident on the nonlinear optical material 1 of the second type phase matching (also referred to as type 2 hereinafter, it is referred to as type 2), 2 Only when the two lights a and b overlap at the same time, the sum frequency light c proportional to the product of the intensities of the two lights a and b is output.

Since the repetition frequency of this sum frequency light c is the repetition frequency (f-Δf) of the sampling light b, the response speed of the photoelectric converter should be higher than this repetition frequency (f-Δf), and the time resolution should be high. Is determined by the pulse width of the sampling light b, so that the pulse waveform of the measured light a can be accurately measured as shown in FIG.

As shown in FIG. 16 (a), the measured light a having an angular frequency ω _D and the sampling light b having an angular frequency ω _S on one surface of the type 2 nonlinear optical material 1 have wavefronts of mutual change. Are incident in a direction orthogonal to each other, the sum frequency light c having the sum angular frequency (ω _S + ω _D ) is output from the other surface under the condition that both lights a and b are phase-matched.

FIG. 16B is a diagram showing the relationship between the optical power P and the angular frequency ω of the measured light a, the sampling light b, and the sum frequency light c.

_Assuming that the light intensity of the sum frequency light c is P _SFG and the light intensities of the measured light a and the sampling light b are P _SIG and P _SAM , the light intensity P _SFG of the sum frequency light c is generally (1) It is shown by the formula.

[0011]   P_SFG= Η · P_SIG・ P_SAM                                … (1) Note that η is the nonlinear conversion efficiency constant, and
A value that is uniquely determined by the type and material of the optical material 1.
is there. This nonlinear conversion efficiency constant η is, for example, 10 ^-Five-10
^-FourAnd a very small value. Therefore, light sample
As a waveform measuring device, this nonlinear conversion efficiency constant η
It is necessary to adopt a large nonlinear optical material 1. Light sun
In the pulling waveform measuring device, the nonlinear optical material 1
Then, KDP (KH₂PO_Four), LN (LiNb
O₃), LT (LiTaO₃), KN (KNbO₃)etc
Has been adopted.

FIG. 17 is a block diagram showing a schematic structure of an optical sampling waveform measuring apparatus in which the above-mentioned type 2 nonlinear optical material 1 is incorporated. The continuous measured light a having the pulse waveform repetition frequency f at the angular frequency ω _D of the light inputted from the outside has its polarization plane in the polarization direction controller 2 with respect to the reference direction (0 degree direction), for example. After being controlled in the direction of 90 degrees, it is incident on the multiplexer 3.

On the other hand, the sampling light source 4 outputs continuous sampling light b having a pulse waveform repetition frequency (f-Δf) at an angular frequency ω _S different from the angular frequency ω _D of the measured light a. As shown in FIG. 15, the pulse width of the sampling light b is set to be much narrower than the pulse width of the measured light a. Sampling light source 4
The polarization direction controller 5 controls the polarization plane of the sampling light b output from the optical axis b to, for example, the reference direction (0 degree direction), and then enters the multiplexer 3.

The multiplexer 3, which is composed of, for example, a beam splitter (BS), causes the half mirror 3a to make the incident light go straight and to reflect it in a right angle direction. Therefore, the sampling light having the polarization plane in the reference direction (0 degree direction) is provided on one surface of the type 2 nonlinear optical material 1 arranged behind the multiplexer 3 and on the optical axis of the sampling light b. b and the measured light a having a polarization plane of 90 directions with respect to the reference direction (0 degree direction) are simultaneously incident.

Therefore, this type 2 nonlinear optical material
From the other side of the material 1, the angular frequency (ω_S+ Ω_D) With
Wave light c is output. Output from nonlinear optical material 1
The sum frequency light c enters the photodetector 7 through the optical filter 6.
Be done. The sum frequency light output from the nonlinear optical material 1
c is the angular frequency ω of each of the two lights b and a described above._S, Ω _D
Angular frequency of sum (ω_S+ Ω_D), Each corner is small
Frequency ω_S, Ω_D2 times the angular frequency 2ω_S, 2ω_D, And
And each angular frequency ω not converted_S, Ω_DIs also included
Then, the optical filter 6 sets these angular frequencies 2ω_S, 2ω_D，
ω_S, Ω_DThe component of is removed.

The photodetector 7 converts the sum frequency light c into an electric signal d and sends it to the next electric signal processing system 8. The electric signal processing system 8 creates an optical pulse waveform of the measured light a expanded in the time direction by the above-mentioned method from the inputted electric signal d having the same waveform as the sum frequency light c shown in FIG. Display output to 9.

[0017]

However, as shown in FIG.
The optical sampling waveform measuring device shown in (1) still has the following problems to be improved.

That is, is the type 2 nonlinear optical material 1
Light intensity P of the sum frequency light c output from _SFGIs also in equation (1)
Samples input to the nonlinear optical material 1 as described
Light intensity P of the reference direction component (for example, 0 degree direction) of the ringing light
_SAMAnd 90 ° to the reference direction of the measured light a.
Minute light intensity P_SIGAnd the nonlinear conversion efficiency η
It

That is, in this optical sampling waveform measuring apparatus, the polarization plane of the sampling light b and the polarization plane of the measured light a input to the nonlinear optical material 1 are linearly polarized light, and 2
When the directions of the polarization planes of the two lights are completely orthogonal to each other, the generated light intensity P _SFG of the sum frequency light c becomes maximum.

Therefore, when it is desired to measure the waveform stably with a little sensitivity, the maximum value of the light intensity P _SFG of the sum frequency light c is obtained before the measurement work of the light pulse waveform of the light to be measured a is started. As described above, it is necessary to adjust each polarization state by each polarization direction controller 2 and 5 (to satisfy the above-mentioned condition) and keep the state stable.

Since the distance between the sampling light source 4 and the polarization direction controller 5 is short, the polarization state of the sampling light b incident on the polarization direction controller 5 varies little, and can be maintained in a constant state almost within the measurement time. . However, when the measured light a is a signal that has passed through a long-distance single-mode optical fiber for a communication network or a signal that has passed through wiring in an optical communication device in which the temperature condition is unstable, the polarization state of the light a changes with time. Due to the large fluctuation, there is a concern that the polarization state may be deviated from the adjustment performed at the start of the measurement work and the measured waveform may fluctuate in a short time.

That is, after the measurement is started, unless the polarization direction controllers 2 and 5 are adjusted as needed, when the polarization state of the measured light a changes, the measured light a output from the polarization direction controller 2 is changed. The 90-degree component of is smaller. This means that the light intensity P _SIG of the measured light a that is reflected by the half mirror-3a of the multiplexer 3 and is incident on the nonlinear optical material 1 fluctuates, and as a result, the measurement accuracy is deteriorated. was there.

Although it is possible to adjust each polarization state at any time after the start of measurement, it is impossible to instantaneously determine whether the signal intensity actually decreases or the polarization state shifts, and it is necessary to make frequent adjustments during measurement. It is practically inconvenient because it will not happen.

The present invention has been made in view of the above circumstances, and separates the sampling light and the measured light for each polarization plane to individually obtain the sum frequency light, and performs complementary processing to obtain even the measured light. It is an object of the present invention to provide an optical sampling waveform measuring device and a polarization separator that can always measure the correct pulse waveform of the measured light even if the polarization state of the above changes with time.

[0025]

In order to solve the above-mentioned problems, in the optical sampling waveform measuring apparatus according to claim 1,
A sampling light source that generates a pulse train of sampling light having a single polarization plane whose pulse width is narrower than that of the light to be measured, and the sampling light and the light to be measured output from this sampling light source are two lights whose polarization planes are different from each other by 90 degrees. A polarization splitter that splits the sampling light and the measured light that are different from each other by 90 degrees and outputs the combined light to separate optical paths, and the polarization surfaces output to the respective optical paths are mutually different. A pair of non-linear optical materials capable of phase-matching the second kind that generate cross-correlation signals of sampling light and light under measurement different from each other by 90 degrees as sum-frequency light, and sum-frequency light output from each non-linear optical material Signal processing for adding the electric signals output from each of the photodetectors and the pair of photodetectors that are converted into the optical receiver, and processing the electric signals after the addition to display the optical pulse waveform of the measured light. And a part.

In the polarization demultiplexer incorporated in the optical sampling waveform measuring apparatus having the above-described structure, the incident sampling light and the measured light have polarization planes of 9 each.
It is split into two lights that differ by 0 degrees. Therefore, a total of 4
Two lights are emitted. Further, two sets (for example, the sampling light having a polarization plane in the reference direction and the 90 degree direction with respect to the reference direction are combined with each other, the sampling light and the measured light are combined so that the polarization planes are orthogonal to each other. A set of the measured light having a plane of polarization, a set of the measured light having a plane of polarization in the reference direction and a set of sambling light having a plane of polarization in the 90 ° direction with respect to the reference direction) is output to different optical paths. It

Then, the respective sets of sampling light and measured light, which are outputted from the respective optical paths and have their polarization planes different from each other by 90 degrees, are incident on the respective non-linear optical materials, and are respectively output as individual sum frequency light. To be Then, each sum frequency light is converted into an electric signal by each individual light receiver and then added, and an optical pulse waveform of the measured light is obtained.

Therefore, even when the polarization state of the measured light changes, in the present configuration, the light intensity of the measured light output from one optical path of the polarization splitter decreases, but it does not output from the other optical path. Since the complementary operation is performed such that the light intensity of the measured light increases, the increase and decrease of the sum frequency light resulting from the change of the polarization state of the measured light is canceled out, and the added electric signal changes. Minutes are hardly included, and the optical pulse waveform of the measured light can be accurately measured.

In the optical sampling waveform measuring apparatus of the second aspect, the sampling light source for generating a pulse train of the sampling light having a pulse width narrower than that of the light to be measured, and the polarization plane of the sampling light output from the sampling light source are controlled in a specific direction. The polarization control unit, and the sampling light and the measured light output from the polarization control unit are respectively separated into two lights having polarization planes different from each other by 90 degrees, and the separated sampling light and the separated light having polarization planes different from each other by 90 degrees. 2 with measuring light
Polarization separators that combine and output to separate optical paths, and a pair of first pair that generate a cross-correlation signal between sampling light and measured light whose polarization planes output to each optical path differ by 90 degrees as sum frequency light. Non-linear optical materials capable of two-phase matching, a pair of photoreceivers for converting the sum frequency light output from each non-linear optical material into an electric signal, and each electric signal output from each photoreceiver are added and added. And a signal processing unit for processing the subsequent electric signal and displaying the optical pulse waveform of the measured light.

In the thus-configured optical sampling waveform measuring apparatus, the polarization controller for controlling the polarization state of the sampling light is interposed between the sampling light source and the polarization splitter. Therefore, regardless of the polarization state of the sampling light, it is possible to set the two light intensities after the splitting to be equal when splitting into two lights whose polarization planes are orthogonal to each other by the polarization splitter.

Therefore, even when the polarization state of the light to be measured changes, in this configuration, the light intensity of the light to be measured output from one optical path of the polarization splitter decreases, but the light from the other optical path outputs. Since the complementary operation is performed such that the light intensity of the measured light increases, the increase and decrease of the sum frequency light resulting from the change of the polarization state of the measured light is canceled out, and the added electric signal changes. Minutes are hardly included, and the optical pulse waveform of the measured light can be accurately measured.

According to another aspect of the optical sampling waveform measuring apparatus of the present invention, a sampling light source for generating a pulse train of sampling light having a single polarization plane having a pulse width narrower than that of the light under measurement, the sampling light output from the sampling light source, and the sampling light Polarization that splits the measurement light into two lights having polarization planes different from each other by 90 degrees, and outputs two separate combinations of the separated sampling light and polarization of the measured light having polarization planes different from each other by 90 degrees. A separator, and a pair of non-linear optical materials capable of phase-matching a second type of pair that generate a cross-correlation signal between the sampling light and the light under measurement whose polarization planes output to the respective optical paths differ from each other by 90 degrees, as sum frequency light, A pair of photodetectors that convert the sum-frequency light output from each nonlinear optical material into an electric signal, and a sampler for each electric signal output from each photodetector. Weighting is performed according to the direction of the incident polarization plane to the polarization splitter of the light, the weighted electrical signals are added, and the added electrical signal is processed to display the optical pulse waveform of the measured light. And a signal processing section for

In the optical sampling waveform measuring apparatus configured as described above, the electric signal before addition is corrected for each electric signal output from each photodetector by correction according to the branching ratio of the sampling light in the polarization separator. By carrying out the steps, the fluctuation of the measurement result is eliminated even if the polarization state of the measured light changes.

In the optical sampling waveform measuring apparatus of the fourth aspect, a pair of optical filters whose pass frequency range is set to the frequency range of the sum frequency light is provided between each nonlinear optical material and each photodetector. .

As described above, the light output from the non-linear optical material includes, in addition to the angular frequency of the sum of the respective frequencies of the measured light and the sampling light, double the angular frequency due to the minute polarization extinction ratio. Component and the component of the measured light and the component of the measured light which are not converted into the sum frequency light and are transmitted through the nonlinear optical material as they are. Therefore, this optical filter is provided to remove these unnecessary components and cut out only the sum frequency light component.

In the optical sampling waveform measuring apparatus of the fifth aspect, a sampling light source for generating a pulse train of the sampling light having a pulse width narrower than that of the light to be measured, and a polarization plane of the sampling light output from the sampling light source are controlled in a specific direction. The polarization control unit, and the sampling light and the measured light output from the polarization control unit are respectively separated into two lights having polarization planes different from each other by 90 degrees, and the separated sampling light and the separated light having polarization planes different from each other by 90 degrees. 2 with measuring light
Polarization separators that combine and output to separate optical paths, and a pair of first pair that generate a cross-correlation signal between sampling light and measured light whose polarization planes output to each optical path differ by 90 degrees as sum frequency light. A non-linear optical material capable of two-phase matching, a pair of photoreceivers for converting the sum frequency light outputted from each non-linear optical material into an electric signal, and provided between each non-linear optical material and each photoreceiver, A pair of optical filters whose passing frequency range is set to the frequency range of the sum frequency light, and which corresponds to the direction of the incident polarization plane with respect to the polarization splitter of the sampling light for each electric signal output from each photoreceiver A signal processing unit that performs weighting, adds the weighted electric signals, processes the added electric signals, and displays the optical pulse waveform of the measured light.

All the above-mentioned functions are added to the optical sampling waveform measuring apparatus configured as described above.

In the optical sampling waveform measuring apparatus of the sixth aspect, the polarization splitter separates the incident sampling light and the measured light into two lights each having a polarization plane different from each other by 90 degrees, and a pair of calcite. A half-wave plate that rotates the polarization states of two lights output from one of the pair of calcites having polarization planes different by 90 degrees from each other by 90 degrees, and the other of the pair of calcites and 1 / It is composed of a pair of condenser lenses that combine and collect the sampling light and the light under measurement, which have different polarization planes output from the two-wavelength plate by 90 degrees.

Further, in the optical sampling waveform measuring apparatus of the seventh aspect, the polarization splitter is provided with a set of the sampling light and the measurement light to which the sampling light and the measurement light are incident and whose polarization planes are different from each other by 90 degrees. And the first calcite that outputs a total of three lights, that is, the sampling light and the measured light whose polarization planes are 90 degrees different from each other, and the polarization states of the three lights output from the first calcite are 90 Rotate 1 degree
It is composed of a two-wave plate and a second calcite that multiplexes the sampling light and the light under measurement whose polarization planes differ from each other by 90 degrees, which are output from the half-wave plate, and outputs the multiplexed light.

Lights thus incident have polarization planes of 9
A polarization separator can be easily constructed by combining a plurality of calcites having a physical property of being split into two lights which are different by 0 degree. Further, by interposing a half-wave plate in the optical path, the optical path length of each light incident on the condenser lens and the second calcite that combine the sampled light and the measured light whose polarization planes are different from each other by 90 degrees can be set. Easy to set equal.

The polarization splitter of claim 8 separates a pair of calcite that separates the incident first light and second light into two lights having polarization planes different from each other by 90 degrees, and of the pair of calcite. Polarization planes output from one of the calcites are 90
1/2 of rotating the polarization state of two different lights by 90 degrees
Wave plate and the other of the pair of calcite and 1 /
It is provided with a pair of condenser lenses for combining and condensing the first light and the second light outputted from the two-wavelength plate and having different polarization planes by 90 degrees.

Further, in the polarization splitter of claim 9, the first light and the second light are incident, and the planes of polarization differ from each other by 90 degrees.
When the first light and the second light of the set are combined, their polarization planes are 9
A first calcite that outputs a total of three lights, a first light and a second light that differ by 0 degrees, and the polarization state of the three lights output from the first calcite are rotated by 90 degrees. The wave plate and the polarization planes output from the half wave plate are 9
It is provided with a second calcite that multiplexes and outputs the first light and the second light that differ by 0 degrees.

According to a tenth aspect of the present invention, there is provided the polarization separator according to
Of the first calcite part that separates the second light and the second light into two lights whose polarization planes are different from each other by 90 degrees, and the polarization planes of the four lights output from this first calcite part are different from each other by 90 degrees. It is provided with a second calcite portion that combines two waves of the first light and the second light and outputs the combined waves to different optical paths.

Further, the polarization separator according to claim 11 is the first
Light and the second light are incident, and a pair of the first light and the second light whose polarization planes are different from each other by 90 degrees are combined, and the first light and the second light whose polarization planes are different from each other by 90 degrees. And a first calcite that outputs a total of three lights, and a first light that is output from the first calcite that is multiplexed with the first light and the second light that have different polarization planes of 90 degrees from each other. It has a calcite of 2.

As described above, in each of the polarization separators of the eighth to eleventh aspects, the incident lights have polarization planes of 9 or more.
A polarization separator can be simply constructed by appropriately combining a plurality of calcite, a half-wave plate, a condenser lens, etc., which have the physical property of splitting into two lights different from each other by 0 degree. The device can be used for various optical devices other than the optical sampling waveform measuring device described above.

[0046]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing the schematic arrangement of an optical sampling waveform measuring apparatus according to the first embodiment of the present invention. The same parts as those of the conventional optical sampling waveform measuring apparatus shown in FIG. 17 are designated by the same reference numerals, and detailed description of the overlapping parts will be omitted.

In this optical sampling waveform measuring apparatus, the polarization splitter 11 and the nonlinear optical member 1 are arranged on the optical axis of the sampling light b ₁ output from the sampling light source 10.
a, a light receiver 7a are provided, and the polarization splitter 11, the nonlinear optical member 1b, and a light receiver 7b are provided on the optical axis of the measured light a input from the outside. Further, a signal processing unit 12 including an adder circuit 12a for processing each electric signal output from each light receiver 7a, 7b and a display processing unit 12b, and a monitor device 13 are provided.

Next, detailed operation of each unit will be described.

A continuous light to be measured a having an angular frequency ω _D input from the outside and a repetition frequency f of a pulse waveform is
It is incident on the polarization separator 11. On the other hand, the sampling light source 10 outputs continuous sampling light b ₁ having a pulse waveform repetition frequency (f−Δf) at an angular frequency ω _S different from the angular frequency ω _D of the measured light a. The pulse width of this sampling light b ₁ is set to be much narrower than the pulse width of the measured light a. As shown in the drawing, the sampling light b ₁ has a single polarization plane that is oriented at 45 ° with respect to the reference direction (0 ° direction). The sampling light b ₁ output from the sampling light source 10 is incident on the polarization splitter 11.

For example, a polarization splitter 11 composed of a polarization beam splitter (PBS) or the like incorporates a half mirror 11a having a surface coated with polarization. This half mirror 11a uses the reference direction (0
The polarized component in the 90 degree direction with respect to the (degree direction) is passed as it is, and the polarized component in the reference direction (0 degree direction) of the incident light is reflected.

Of the sampling light b ₁ output from the sampling light source 10 and having a polarization plane of approximately 45 degrees, the polarization component b _{2 in} the 90 degrees direction and the reference direction (0 degrees direction) in the measured light a. The polarization component a ₂ is incident on the type 2 nonlinear optical member 1a. On the other hand, the sampling light b ₁
Of these, the polarization component b _{3 in} the reference direction and the polarization component a _{3 in} the 90 ° direction of the measured light a are incident on another type 2 nonlinear optical member 1b.

The polarization planes of the non-linear optical member 1a are 9
The sampling light b ₂ and the light to be measured a _{2 which} are set in directions different from each other by 0 degree are input, so that the phase matching is satisfied and the sum frequency having the angular frequency (ω _S + ω _D ) from the type 2 nonlinear optical member 1 a The light c ₂ is output to the next light receiver 7a.

Similarly, the non-linear optical member 1b has sampling light beams b whose polarization planes are set in directions different from each other by 90 degrees.
₃ and the light to be measured a ₃ are input, the phase matching is satisfied, and the angular frequency (ω _S
The sum frequency light c ₃ having + ω _D ) is output to the next photodetector 7b.

The photodetectors 7a and 7b convert the incident sum-frequency lights c ₂ and c ₃ into electric signals d ₂ and d ₃ , respectively, and send them to the signal processing unit 12. The respective electric signals d ₂ and d ₃ input into the signal processing unit 12 are signal-added by the adding circuit 12a and input to the display control unit 12b as a new electric signal d ₄ . The display control unit 12b obtains the optical pulse waveform of the measured light a by performing the envelope detection of the electric signal d ₄ after the addition, and outputs the waveform to the monitor device 13 for display.

In the optical sampling waveform measuring instrument having such a configuration, the polarization plane of the sampling light b ₁ output from the sampling light source 10 is approximately 45 degrees from the reference direction, and the half mirror 11a of the polarization splitter 11 is used. Is about 45 with respect to the optical axes of the sampling light b ₁ and the measured light a.
The intensity of the transmitted light and the intensity of the reflected light at the polarization splitter 11 are almost equal because they are set in the degree direction.

That is, of the sampling light b ₁ separated by the polarization splitter 11, the light intensity of the polarization component b _{3 in} the reference direction and the light intensity of the polarization component b _{2 in} the 90 ° direction with respect to the reference direction are almost the same. Are equal.

On the other hand, since the polarization state of the measured light a is disturbed by disturbance, the light intensity of the measured light a ₂ having the polarization plane of the reference direction output from the polarization splitter 11 and the reference direction are different. On the other hand, the measured light a ₃ having a polarization plane in the direction of 90 degrees
Of the non-linear optical material 1a on which the increased measured light a ₂ (a ₃ ) is incident,
The intensity of the sum frequency light c ₂ (c ₃ ) emitted from (1b) is increased, and the reduced light to be measured a ₃ (a ₂ ) is emitted from the nonlinear optical material 1b (1a) which is incident. The light intensity of the sum frequency light c ₃ (c ₂ ) becomes small.

Therefore, each nonlinear optical material 1
Sum frequency light c output from a and 1b ₂, C₃The light intensity of
It changes depending on the polarization state of the measured light a. However, Washu
Wave light c₂, C₃Is photoelectrically converted by each of the light receivers 7a and 7b.
Qi signal d₂, D₃Electrical signal d_FourOriginally 1
Since it is a signal obtained by branching two measured lights a,
Issue d₂And electrical signal dd₃Perform complementary operations, and
Changes in the waveform of the measurement pulse due to changes in the polarization state of the constant light a
Will be offset.

That is, since the electric signal d ₄ obtained by adding the electric signals d ₂ and d ₃ is stabilized, the pulse waveform of the light to be measured a can be accurately measured in the display section 12b regardless of the polarization state.

Up to this point, the branching ratio of the sampling light b _{1 in} the polarization splitter 11 has been set to approximately 1: 1. However, in the present configuration, the effect of the branching ratio of the sampling light b _{1 on} the waveform measurement is quantified. Estimate below.

That is, the sum frequency light c output from the nonlinear optical material 1a (lb) capable of achieving the type II phase matching
The light intensity P _SFG of ₂ (c ₃ ) is the nonlinear optical material 1a (1
Let b _SIG and P _SAM be the light intensities of the measured light a and the sampling light b ₁ that have the polarization planes orthogonal to each other and are input to b). P _SFG = η · P _SIG · P _SAM (2) Become. However, η is a nonlinear conversion efficiency constant.

Now, here again, the sampling light b₁of
Polarization component b in the 90 degree direction transmitted through the polarization separator 11a₂
Light intensity of n · P_SAM, While sampling light b₁
Polarization component b in the reference direction reflected by the polarization separator 11a
₃Light intensity of (1-n) · P _SAM(However, 0 ≦ n ≦ 1)
Expressed as, the light intensity P_SAMCan be expressed as

P _SAM = [nP _SAM ] ₉₀ + [(1-n) P _SAM ] ₀ (3) However, [] ₉₀ indicates the light intensity in the 90 ° direction, and [] ₀
The light intensity in the reference direction (0 degree direction) is shown.

Similarly, assuming that the polarization state of the light under measurement a changes, the light intensity of the polarization component a ₂ of the light under measurement a reflected by the polarization splitter 11a in the reference direction is m · P _SIG. , The light intensity of the polarization component a ₃ in the 90-degree direction of the measured light a transmitted through the polarization splitter 11a is expressed as (1-m) · P _SIG (where 0 ≦ m ≦ 1), the light intensity P _SIG can be expressed as follows.

P _SIG = [mP _SIG ] ₀ + [(1-m) P _SIG ] ₉₀ (4) However, [] ₉₀ indicates the light intensity in the 90 degree direction, and [] ₀
The light intensity in the reference direction (0 degree direction) is shown.

Therefore, the equation (5) is obtained from the equations (2), (3) and (4).

P _SFG = η · {[nP _SAM · mP _SIG ] ₉₀ + [(1-n) · (1-m) · P _SAM · P _SIG ] ₀ } (5) where the nonlinear conversion efficiency η Is a constant, so only the essential ones required now are taken out, and the formula relating to the light intensity P _SFG obtained by summing the sum frequency light c ₂ and the sum frequency light c ₃ is rearranged.
Equation (6) is obtained.

P _SFG ∝ (2 nm−n−m + 1) P _SAM · P _SIG (6) In FIG. 2A, m is fixed to 0 or 1, and n is set from 0 to 1.
FIG. 6 is a schematic diagram of the total change in light intensity of the sum frequency light c ₂ and the sum frequency light c ₃ obtained when the light intensity is changed up to equation (6). On the other hand, FIG. 2B shows a case where only sampling light having a polarization plane in the reference direction (or a direction different from the reference direction by 90 degrees) is used, that is, n is 1 (or 0). 2) is a schematic diagram showing an output change of the obtained sum frequency light intensity when m is changed from 0 to 1 by fixing only to).

When n or m changes from this FIG. 2 (a), the sum frequency light intensity P _{SFG, which} is the sum of the sum frequency light c ₂ and the sum frequency light c ₃ , fluctuates greatly, while what value of m ( Even if the polarization state of the measured light changes, n is almost 0.
This method has a point that the total light intensity P _SFG of the sum-frequency light c ₂ and the sum-frequency light c ₃ is constant when 5 (the branching ratio in the polarization splitter is 1: 1). It can be understood. However, it can be understood that such a point does not exist in the conventional method, as shown in FIG. 2B, and it is difficult to avoid the fluctuation of the measurement waveform due to the fluctuation of the polarization state.

It will be explained again with reference to FIG.

FIG. 3 shows the sum frequency light c ₂ and the sum frequency light c when m changes from 0 to 1 with respect to the value of n based on the equation (6), that is, from the possible minimum value to the maximum value. _This is an example of calculation of the total light intensity P _SFG with ₃ and FIG. 4 shows a case where m changes from 0 to 1 when n is fixed in the range of 0.4 to 0.6. FIG. 5 is an enlarged view of the central portion of the calculation example of the fluctuation range of the total light intensity P _SFG of the obtained sum frequency light c ₂ and the sum frequency light c ₃ .

For example, assuming that the allowable value of the fluctuation of the optical waveform caused by the fluctuation of the polarization of the measured light a is 1%, the range from FIG. 5 to n can be obtained as follows.

0.4795 ≦ n ≦ 0.5025 (7) In other words, if the value of n is in the range of (7), the optical pulse can be measured within 1% of the waveform fluctuation. I am obsessed with.

This value requires a very high degree of adjustment work in order to obtain it by adjusting only the polarization plane of light, but it is a value that can be easily adjusted by using the weighting process of the electric stage.
Although the permissible value of the optical waveform fluctuation is 1% here, it goes without saying that the larger the permissible value, the larger the range of equation (7) becomes.

Therefore, this method is used as shown in FIG.
Individual sum-frequency lights c ₂ and c ₃ output from the respective nonlinear optical materials 1a and 1b using the individual nonlinear optical materials 1a and 1b.
It can be understood that the optical pulse waveform of the measured light a can be measured with high accuracy without being affected by the change in the polarization state of the measured light a by adding the light intensities of 1. As described above, in the optical sampling waveform measuring apparatus of the first embodiment shown in FIG. 1, the optical pulse waveform of the measured light a is measured with high accuracy without being influenced by the polarization state of the measured light a for the above reasons. It will be possible.

(Second Embodiment) FIG. 6 is a block diagram showing the schematic arrangement of an optical sampling waveform measuring apparatus according to the second embodiment of the present invention. The same parts as those of the optical sampling waveform measuring apparatus of the first embodiment shown in FIG. 1 are designated by the same reference numerals. Therefore, detailed description of the overlapping portions is omitted.

In the optical sampling waveform measuring apparatus of the second embodiment, the polarization control section 14 composed of, for example, a half-wave plate or a quarter-wave plate between the sampling light source 10 and the polarization splitter 11. Has been inserted. The polarization controller 14 has a function of setting the direction of the polarization plane of the sampling light b ₄ output from the sampling light source 10 to the direction of 45 degrees with respect to the reference direction (direction of 0 degrees). Therefore, the direction of the plane of polarization of the sampling light b ₅ incident on the polarization splitter 11 from the polarization controller 14 is accurately set to the direction of 45 degrees.

In this case, they are separated by the polarization separator 11,
The light intensities P of the sampling lights b ₂ and b ₃ in the 90 ° direction and the reference direction, which are input to the nonlinear optical members 1a and 1b, respectively.
_{Since the SAMs} can be made equal, it is possible to suppress the fluctuation of the added electric signal d ₄ of each sum frequency light c ₂ , c ₃ . Therefore, it is possible to further improve the measurement accuracy of the optical pulse waveform of the measured light a obtained from the signal obtained by adding these.

Further, in this case, it is not necessary to set the polarization plane of the sampling light b ₄ output from the sampling light source 10 particularly in the direction of 45 degrees.

(Third Embodiment) FIG. 7 is a block diagram showing the schematic arrangement of an optical sampling waveform measuring apparatus according to the third embodiment of the present invention. The same parts as those of the optical sampling waveform measuring apparatus of the first embodiment shown in FIG. 1 are designated by the same reference numerals. Therefore, detailed description of the overlapping portions is omitted.

In the signal processing section 12 of the optical sampling waveform measuring apparatus according to the third embodiment, a pair of weighting circuits 15a and 15 are provided in addition to the adding circuit 12a and the display control section 12b.
b is incorporated.

That is, in the first embodiment, the sampling light b ₁ output from the sampling light source 10
However, since the transmitted light intensity and the reflected light intensity are almost equal in the polarization separator 11, the pulse waveform of the light to be measured a can be accurately measured by adding the respective sum frequency lights P _SFG .

However, in the case of a measuring instrument in which the angle direction of the polarization plane of the sampling light b ₁ is deviated by more than 45 degrees (n = 0.5), when high accuracy is desired, or when the sum of the nonlinear optical materials 1a and 1b is added. If the frequency light generation efficiency is not equal,
It is not possible to suppress the fluctuation width within the desired allowable value only by adding the sum frequency lights c ₂ and c ₃ .

Therefore, as described in the first embodiment, in the present embodiment, the weighting circuits 15a and 15 are applied to the electric signals d ₂ and d ₃ output from the photodetectors 7a and 7b.
By weighting b according to the branching ratio in the polarization splitter, the influence of the polarization state fluctuation of the measured light on the measurement result is suppressed as much as possible.

(Fourth Embodiment) FIG. 8 is a block diagram showing the schematic arrangement of an optical sampling waveform measuring apparatus according to the fourth embodiment of the present invention. The same parts as those of the optical sampling waveform measuring apparatus of the first embodiment shown in FIG. 1 are designated by the same reference numerals. Therefore, detailed description of the overlapping portions is omitted.

In the optical sampling waveform measuring apparatus of the fourth embodiment, each nonlinear optical member 1a. The optical filters 16a and 16b are provided between the optical fiber 1b and the respective photodetectors 7a and 7b
Has been inserted.

As shown in FIG. 9B, the passing angular frequency ranges of the optical filters 16a and 16b are sum frequency lights c ₂ and c.
Sampling light b including the angular frequency (ω _S + ω _D ) of ₃
The angular frequency 2ω _S twice the angular frequency ω _S of ₁ , the angular frequency 2ω _D twice the angular frequency ω _D of the light to be measured a, and the angular frequency (ω _S + ω _D ) of the sum and each angle double Frequency 2ω _S , 2ω
_The angular frequency range is set so that the angular frequencies ω _S and ω _D that have not been converted to _D and ω are removed.

That is, as shown in FIGS. 9A and 9B, the sum frequency lights c ₂ and c ₃ output from the nonlinear optical materials 1a and 1b are included in the sampling light b ₁ and the measured light a. In addition to the angular frequency (ω _S + ω _D ) of the sum of the frequencies, the angular frequency 2 that is twice the angular frequency due to the minute phase mismatch 2
ω _S , 2ω _D , and each unconverted angular frequency ω _S ,
Since ω _{D is} also included, each optical component having these angular frequencies can be removed by the optical filters 16a and 16b.

As a result, the measurement accuracy of the pulse waveform of the measured light a can be further improved.

(Fifth Embodiment) FIG. 10 is a block diagram showing the schematic arrangement of an optical sampling waveform measuring apparatus according to the fifth embodiment of the present invention. The same parts as those of the embodiments shown in FIGS. 1, 6, 7, and 8 are designated by the same reference numerals. Therefore, detailed description of the overlapping portions is omitted.

The polarization plane of the sampling light b ₄ output from the sampling light source 10 is set to 45 by the polarization controller 14, and the sampling light b ₄ is incident on the polarization splitter 11 as new sampling light b ₅ . The measured light a input from the outside is directly incident on the polarization splitter 11.

The sum frequency lights c ₂ and c ₃ output from the nonlinear optical members 1a and 1b are optical filters 16a and 16b,
Angular frequencies ω _S , ω of the sampling light b ₅ and the measured light a
_The optical components of the angular frequencies 2ω _S and 2ω _D that are twice as large as _D and the unconverted angular frequencies ω _S and ω _D are removed, and the optical receivers 7a. 7b is the sampling light b ₅ , and the angular frequency (ω _S + ω _D ) of the sum of the angular frequencies ω _S and ω _D of the measured light a.
The sum frequency lights c ₂ and c ₃ having Each light receiver 7
Reference numerals a and 7b convert the received sum frequency lights c ₂ and c ₃ into electric signals d ₂ and d ₃ , respectively.

Each electric signal d _{2 of} each sum frequency light c ₂ , c ₃ .
d ₃ is the weighting circuits 15 a, 1 in the signal processing unit 12.
5b, the sampling light b ₅ is weighted according to the direction of the incident polarization plane of the polarization separator 11, and then converted into one electric signal d ₄ by the adder circuit 12a. The display control unit 12b obtains the optical pulse waveform of the measured light a by performing the envelope detection of the electric signal d ₄ after the addition, and outputs the waveform to the monitor device 13 for display.

In the optical sampling waveform measuring apparatus of the fifth embodiment configured as described above, in addition to the basic configuration as the optical sampling waveform measuring apparatus shown in the first embodiment of FIG. 1, FIGS. The polarization controller 14, the weighting circuits 15a and 15b, and the optical filter 16 of each embodiment shown in FIG.
Since a and 16b are incorporated, the measurement accuracy of the optical pulse waveform of the measured light a can be further improved.

(Sixth Embodiment) FIG. 11 shows a sixth embodiment of the present invention.
It is a schematic diagram which shows schematic structure of the polarization splitter incorporated in the optical sampling waveform measuring apparatus of embodiment. This polarization separator is composed of a pair of calcites 17a arranged in the same crystal direction,
17b, a half-wave plate 21 attached to the emission surface of one of the pair of calcites 17a, 17b, and one output from the half-wave plate 21 and the other calcite 17b. It is composed of a pair of condenser lenses 18a and 18b which combine and condense light.

The light to be measured a inputted from the outside is the calcite 1
At 7a, the light a ₃ whose polarization plane is 90 degrees to the reference direction (0 degree direction) and the light a ₂ whose polarization plane is the reference direction (0 degree direction) are separated. Similarly, the light b ₂ polarization is 90 ° direction with respect to the reference direction (0 ° direction) by the sampling light b ₁ whose polarization plane output from the sampling light source 10 faces the 45 degree direction calcite 17b, polarized The wave front is separated into the light b _{3 in the} reference direction (0 degree direction).

The polarization plane output from the calcite 17a is 90
The light to be measured a ₃ in the degree direction is incident on one of the condenser lenses 18a after the polarization direction is rotated by 90 degrees in the reference direction (0 degree direction) by the ½ wavelength plate 21. The other calcite 17
The sampling light b ₂ having a polarization plane of 90 degrees output from b is directly incident on one condenser lens 18a. Therefore, the light to be measured a ₃ whose polarization plane is converted to the reference direction (0 degree direction) and the polarization plane are 90 degrees by this condenser lens 18a.
The sampling light b ₂ which is still in the direction of the angle is multiplexed and is incident on the next nonlinear optical material 1b.

The sampling light b ₃ whose polarization plane is the reference direction (0 ° direction) output from the calcite 17b is directly incident on the other condenser lens 18b. In addition, the polarization plane output from the calcite 17a is the measured light a in the reference direction (0 degree direction).
Reference numeral ₂ denotes a half-wave plate 21 whose polarization direction is rotated by 90 degrees in the direction of 90 degrees and then is incident on the other condenser lens 18b.
Therefore, the plane of polarization is 90 degrees with this condenser lens 18b.
The light to be measured a ₂ that has been converted to the direction of the light and the sampling light b ₃ whose plane of polarization is still in the reference direction (direction of 0 degrees) are combined and incident on the next nonlinear optical material 1a.

Thus, the two calcites 17a and 17b are
And one half-wave plate 21 and two condenser lenses 18
a and 18b are used to set the optical path lengths of the lights incident on the condenser lenses 18a and 18b to be equal,
Polarization Beam Splitter (PBS) of First to Fifth Embodiments
It is possible to exhibit the same function as that of the polarization separator 11 configured by.

(Seventh Embodiment) FIG. 12A is a schematic diagram showing a schematic configuration of a polarization splitter incorporated in an optical sampling waveform measuring apparatus of a seventh embodiment of the present invention. Also,
FIG. 12B is a plan view for explaining the traveling direction of each light in this polarization splitter. This polarization separator is composed of a first calcite 19a, a second calcite 19b, a pair of reflecting mirrors 20a and 20b, and a half-wave plate 20a arranged on the same optical axis. It is configured.

In FIGS. 12 (a) and 12 (b), the light to be measured a incident on the first calcite 19a is light a ₃ whose polarization plane is 90 ° in the first calcite 19a and the polarization plane is the reference direction. It is separated into light (a 0 direction) a ₂ . Similarly, the sampling light b ₁ output from the sampling light source 10 whose polarization plane is oriented in the direction of 45 degrees is the light b ₂ whose polarization plane is in the direction of 90 degrees with respect to the reference direction (0 degree direction) in the first calcite 19a.
And the plane of polarization is separated into the light b _{3 in the} reference direction (0 degree direction).

At the exit of the first calcite 19a, the sampling light b ₂ in the 90 ° direction and the measured light a _{2 in the} reference direction (0 ° direction) are combined, and the polarization direction is changed by the ½ wavelength plate 21a. After being rotated by 90 degrees, the light enters the nonlinear optical material 1a via the reflecting mirror 20a.

The measured light a ₃ in the 90-degree direction output from the first calcite 19a is rotated by 90 degrees in the reference direction (0-degree direction) in the polarization direction by the ½ wavelength plate 21a.
It is refracted at the entrance of the second calcite 19b and goes straight inside the second calcite 19b. The sampling b ₃ in the 0-degree direction output from the first calcite 19a is the half-wave plate 2
After polarization direction is rotated 90 degrees in the 90 degree direction in 1a, straight through the second calcite 19b, and outputs the same position and the light to be measured a ₃ of the previous reference direction (0 ° direction).

[0105] As a result, the sump link optical a ₃ to the reference direction (0 ° direction) measured light a _3, which is converted to the converted 90-degree direction at the exit of the second calcite 19b is combined,
The light enters the nonlinear optical material 1b via the reflecting mirror 20b.

In the optical path length from this polarization separator to each of the nonlinear optical materials 1a and 1b, the second calcite 19
Since an optical path difference substantially equal to the dimension of b is generated, the installation positions of the respective nonlinear optical materials 1a and 1b are strictly adjusted so that both optical path lengths are equal.

Thus, the two calcites 19a and 19b
By setting the dimensions of each part so that the lights traveling through the optical axis and inside the half-wave plate 21a are combined at the exit,
In the first to fifth embodiments, the polarization beam splitter (P
The function similar to that of the polarization separator 11 configured by BS) can be exerted.

(Eighth Embodiment) FIG. 13 is a schematic diagram showing a schematic configuration of a polarization separator incorporated in an optical sampling waveform measuring apparatus of an eighth embodiment of the present invention. The same parts as those of the polarization separator of the sixth embodiment shown in FIG. 11 are designated by the same reference numerals, and detailed description of the overlapping parts will be omitted.

The polarization splitter according to the eighth embodiment is
A pair of calcites 17a and 17b constituting the first calcite portion arranged in the same crystal direction and the pair of calcites 17
a, 17b and a pair of other calcites 22a, 22b which are arranged in a direction orthogonal to the second calcite part.

The measured light a input from the outside is the calcite 1
At 7a, the light a ₃ whose polarization plane is 90 degrees to the reference direction (0 degree direction) and the light a ₂ whose polarization plane is the reference direction (0 degree direction) are separated. Similarly, the light b ₂ polarization is 90 ° direction with respect to the reference direction (0 ° direction) by the sampling light b ₁ whose polarization plane output from the sampling light source 10 faces the 45 degree direction calcite 17b, polarized The wave front is separated into the light b _{3 in the} reference direction (0 degree direction).

The polarization plane output from the calcite 17a is 90
The measured light a _{3 in the} direction of degree travels straight in the next calcite 22a. Further, the sampling light b ₃ whose polarization plane is output from the calcite 17b and has the reference direction (0 degree direction) is refracted by the calcite 22a and is output from the same position as the measured light a _{3 described} above. Therefore, the measured light a ₃ having a polarization plane of 90 ° and the sampling light b ₃ having a polarization plane of the reference direction (0 ° direction) are combined and incident on the next nonlinear optical material 1 b.

The polarization plane output from the calcite 17b is 90
The sampling light b _{2 in the} degree direction travels straight in the next calcite 22b. Further, the sampling light b ₂ output from the calcite 17 a and having the polarization plane of the reference direction (0 ° direction) is the calcite 22.
It is refracted by b and is output from the same position as the sampling light b ₂ . Therefore, the sampling light b ₂ having a polarization plane of 90 degrees and the measured light a ₂ having a polarization plane of the reference direction (0 degree direction) are combined and incident on the next nonlinear optical material 1 a.

Thus, the four calcites 17a, 17
The polarization beam splitter (PBS) according to the first to fifth embodiments is configured by setting the outer diameter dimension so that the lights passing through the optical axes or inside b, 18a, and 18b are combined at the exit. The function similar to that of the polarization separator 11 can be exerted.

(Ninth Embodiment) FIG. 14A is a schematic diagram showing a schematic configuration of a polarization separator incorporated in an optical sampling waveform measuring apparatus of a ninth embodiment of the present invention. Also,
FIG. 14B is a plan view for explaining the traveling direction of each light in this polarization splitter. The same parts as those of the polarization separator of the seventh embodiment shown in FIG. 12 are designated by the same reference numerals, and detailed description of the overlapping parts will be omitted.

The polarization splitter according to the ninth embodiment is
As shown in the figure, the half-wave plate 21a is removed from the polarization separator of the seventh embodiment shown in FIG.

That is, in FIGS. 12 (a) and 12 (b),
Measured light a incident on the first calcite 19a is separated into a light a _3, and the light a ₂ of polarization is the reference direction (0 ° direction) is the polarization plane by 90 ° direction in the first calcite 19a It Similarly, the plane of polarization output from the sampling light source 10 is 45
The sampling light b ₁ directed in the direction of degree is the first calcite 19a.
A light b ₂ whose polarization plane is 90 degrees to the reference direction (0 degree direction) and a light b ₃ whose polarization plane is the reference direction (0 degree direction)
And separated.

At the exit of the first calcite 19a, the sampling light b ₂ in the 90 ° direction and the measured light a _{2 in the} reference direction (0 ° direction) are combined, and the nonlinear optical material 1a is passed through the reflecting mirror 20a. Is incident on.

Further, the light to be measured a ₃ in the 90-degree direction output from the first calcite 19a goes straight in the second calcite 19b. The 0 ° direction sampling b ₃ output from the first calcite 19a is refracted at the entrance of the second calcite 19b and output from the same position as the measured light a _{3 in} the 90 ° direction.

As a result, at the exit of the second calcite 19b, 9
0 ° and sump link optical a ₃ in the direction of the light to be measured a ₃ and a reference direction (0 ° direction) are multiplexed, is incident to the nonlinear optical material 1b through the reflecting mirror 20b.

In the optical path length from this polarization separator to each of the nonlinear optical materials 1a and 1b, the second calcite 19
Since an optical path difference almost equal to the dimension b is generated,
Similarly to the polarization separator of the seventh embodiment shown in FIG. 7, the installation positions of the respective nonlinear optical materials 1a and 1b are strictly adjusted so that both optical path lengths become equal.

Thus, the two calcites 19a and 19b are
By setting the dimensions of the respective parts so that the respective lights traveling through the optical axis and inside are combined at the exit, a polarization beam splitter 11 composed of a polarization beam splitter (PBS) in the first to fifth embodiments is provided. The same function can be exerted.

The polarization splitter formed by combining a plurality of calcites shown in FIGS. 11, 12, 13, and 14 can be incorporated in an optical processing device other than the above-mentioned optical sampling waveform measuring device. Is.

[0123]

As described above, in the optical sampling waveform measuring apparatus of the present invention, one polarization splitter and a pair of type 2 non-linear optical materials are incorporated to obtain sampling light and measured light. Is separated for each polarization plane to individually obtain sum frequency light, and these are added later.

Therefore, even if the polarization plane of the measured light fluctuates with time, even if the direction of the polarization plane of the sampling light is not set accurately,
It is possible to carry out the measurement of the optical pulse waveform with high accuracy for the measured light.

Further, the sampling light and the light to be measured are separated into two lights having polarization planes different from each other by 90 degrees, and thereafter, two separated waves are combined with the separated sampling light having polarization planes different from each other by 90 degrees to separate them. The polarization splitter that outputs to the optical path of is composed of multiple calcite.

As described above, the polarization splitter can be easily constructed by combining a plurality of calcites having the physical property of splitting the incident light into two lights having polarization planes different from each other by 90 degrees. Further, this polarization splitter can be used in various optical devices other than the above-mentioned optical sampling waveform measuring device.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an optical sampling waveform measuring apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the relationship between the light intensity of the sum frequency light output from the polarization splitter and the branching ratio of the incident light.

FIG. 3 is a diagram showing the relationship between the light intensity of the sum frequency light and the branching ratio of the measured light using the branching ratio of the sampling light as a parameter.

FIG. 4 is a diagram showing the relationship between the fluctuation range of the light intensity of the sum frequency light and the branching ratio of the sampling light.

FIG. 5 is an enlarged view showing a main part of the graph shown in FIG.

FIG. 6 is a block diagram showing a schematic configuration of an optical sampling waveform measuring apparatus according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a schematic configuration of an optical sampling waveform measuring apparatus according to a third embodiment of the present invention.

FIG. 8 is a block diagram showing a schematic configuration of an optical sampling waveform measuring apparatus according to a fourth embodiment of the present invention.

FIG. 9 is a characteristic diagram for explaining the effect of an optical filter incorporated in the measurement device.

FIG. 10 is a block diagram showing a schematic configuration of an optical sampling waveform measuring apparatus according to a fifth embodiment of the present invention.

FIG. 11 is a schematic diagram showing a schematic configuration of a polarization splitter incorporated in an optical sampling waveform measuring apparatus according to a sixth embodiment of the present invention.

FIG. 12 is a schematic diagram showing a schematic configuration of a polarization separator incorporated in an optical sampling waveform measuring apparatus according to a seventh embodiment of the present invention.

FIG. 13 is a schematic diagram showing a schematic configuration of a polarization separator incorporated in an optical sampling waveform measuring apparatus according to an eighth embodiment of the present invention.

FIG. 14 is a schematic diagram showing a schematic configuration of a polarization separator incorporated in an optical sampling waveform measuring apparatus according to a ninth embodiment of the present invention.

FIG. 15 is a diagram for explaining the measurement principle of optical pulse waveform measurement of an optical signal using sum frequency light.

FIG. 16 is a diagram for explaining the optical characteristics of a type 2 nonlinear optical material.

FIG. 17 is a block diagram showing a schematic configuration of a conventional optical sampling waveform measuring device.

[Explanation of symbols]

1a, 1b ... Nonlinear optical material 7a, 7b ... Photodetector 10 ... Sampling light source 11 ... Polarization splitter 12 ... Signal processing unit 12a ... Addition circuit 12b ... Display control unit 13 ... Monitor device 14 ... Polarization control units 15a, 15b ... Weighting circuits 16a, 16b ... Optical filters 17a, 17b, 22a, 22b ... Calcite 18a, 18b ... Condensing lens 19a ... First calcite 19b ... Second calcite 20a, 20b ... Plane mirror 21, 21a ... 1/2 wave plate a, a ₂ , a ₃ ... Measured light b ₁ , b ₂ , b ₃ ... Sampling light c ₂ , c ₃ ... Sum frequency light d ₂ , d ₃ , d ₄ ... Electrical signal

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshinobu Otsubo             5-10-10 Minamiazabu, Minato-ku, Tokyo Henri             Tsu Co., Ltd. (72) Inventor Hidehiko Takara             3-19-3 Nishi-Shinjuku, Shinjuku-ku, Tokyo Japan             Telegraph and Telephone Corporation (72) Inventor Satoru Kawanishi             3-19-3 Nishi-Shinjuku, Shinjuku-ku, Tokyo Japan             Telegraph and Telephone Corporation F-term (reference) 2G065 AA12 AB09 AB16 BA01 BB14                       BB50 BC04 DA13                 2H099 AA01 BA17 CA05 CA08 DA05                 2K002 AA04 AB12 BA03 HA19

Claims (11)

[Claims] 1. A sampling light source (10) for generating a pulse train of sampling light having a single polarization plane whose pulse width is narrower than that of the light to be measured, and the sampling light output from the sampling light source and the light to be measured are mutually polarized. A polarization splitter (11) which splits into two lights having wavefronts different from each other by 90 degrees, and outputs two separate combined waves of the separated sampling light and measured light having polarization surfaces different from each other by 90 degrees And a pair of second-type phase-matching nonlinear optical materials (1a, 1a, which generate cross-correlation signals of sampling light and measured light whose polarization planes output to the respective optical paths differ from each other by 90 degrees, as sum frequency light. 1b), a pair of photodetectors (7a, 7b) that convert the sum frequency light output from each of the nonlinear optical materials into an electric signal, and the electric signals output from the photodetectors, and after addition Electrical signal A signal processing unit processing and displays light pulse waveform of the light to be measured (12) and the optical sampling waveform measuring apparatus having a. 2. A sampling light source (10) for generating a pulse train of sampling light having a pulse width narrower than that of the light to be measured, and a polarization controller (14) for controlling the polarization plane of the sampling light output from the sampling light source in a specific direction. ) And the sampling light and the measured light output from the polarization control unit are respectively separated into two lights whose polarization planes are different from each other by 90 degrees, and the separated sampling light and the measured light whose polarization planes are different from each other by 90 degrees. A polarization splitter (11) that outputs two combined waves of light and separate optical paths and outputs the cross-correlation signals of the sampled light and the measured light whose polarization planes are 90 degrees different from each other. A pair of non-linear optical materials (1a, 1b) capable of phase-matching the second type generated as frequency light, and a pair of photodetectors (7a, 7a, 1a, 1b) for converting the sum frequency light output from each of the non-linear optical materials into an electric signal. 7b ), And a signal processing unit (12) for adding the respective electric signals output from the respective light receivers, processing the electric signals after the addition, and displaying the optical pulse waveform of the measured light. Waveform measuring device. 3. A sampling light source (10) for generating a pulse train of sampling light having a single polarization plane whose pulse width is narrower than that of the light to be measured, and the sampling light output from this sampling light source and the light to be measured are mutually polarized. A polarization splitter (11) that splits into two lights having wavefronts different from each other by 90 degrees and outputs two separate combinations of the separated sampling light and measured light having polarization surfaces different from each other by 90 ° And a pair of second-type phase-matching nonlinear optical materials (1a, 1a, which generate a cross-correlation signal between the sampling light and the light under measurement, whose polarization planes output to the respective optical paths differ from each other by 90 degrees, as sum frequency light. 1b), a pair of photodetectors (7a, 7b) for converting the sum frequency light output from each of the nonlinear optical materials into an electric signal, and the sampling light for each electric signal output from each of the photodetectors. Weighting is performed according to the direction of the incident polarization plane with respect to the polarization splitter, the weighted electric signals are added, and the added electric signal is processed to display the optical pulse waveform of the measured light. An optical sampling waveform measuring device including a signal processing section (12) for 4. A pair of optical filters (16a, 16b) provided between each of the non-linear optical materials and each of the light receivers and having a pass frequency range set to the frequency range of the sum frequency light. The optical sampling waveform measuring device according to any one of claims 1 to 3, 5. A sampling light source (10) for generating a pulse train of sampling light having a pulse width narrower than that of the light to be measured, and a polarization controller (14) for controlling the polarization plane of the sampling light output from the sampling light source in a specific direction. ) And the sampling light and the measured light output from the polarization control unit are respectively separated into two lights whose polarization planes are different from each other by 90 degrees, and the separated sampling light and the measured light whose polarization planes are different from each other by 90 degrees. A polarization splitter (11) that outputs two combined waves of light and separate optical paths and outputs the cross-correlation signals of the sampled light and the measured light whose polarization planes are 90 degrees different from each other. A pair of non-linear optical materials (1a, 1b) capable of phase-matching the second type generated as frequency light, and a pair of photodetectors (7a, 7a, 1a, 1b) for converting the sum frequency light output from each of the non-linear optical materials into an electric signal. 7b ), A pair of optical filters (16a, 16b) provided between each of the non-linear optical materials and each of the light receivers, the pass frequency range of which is set to the frequency range of the sum frequency light, and each of the light receivers. The weighted electrical signals are added to each of the electrical signals output from the sampled light according to the direction of the incident polarization plane with respect to the polarization splitter of the sampling light, and the electrical signals after addition are added. An optical sampling waveform measuring device comprising: a signal processing unit (12) for processing the signal to display the optical pulse waveform of the measured light. 6. The pair of calcites that separates the incident sampling light and measured light into two lights each having a polarization plane different by 90 degrees from each other.
(17a, 17b) and the polarization state of two lights output from one of the pair of calcites, the polarization planes of which differ from each other by 90 degrees.
A half-wave plate (21) rotated by one degree, the other calcite of the pair of calcite and the half
6. A pair of condensing lenses (18a, 18b) for condensing and combining the sampling light and the measured light whose polarization planes output from the wave plate are different by 90 degrees, and are composed of a pair of condensing lenses (18a, 18b). The optical sampling waveform measuring device according to any one of 1. 7. The polarization splitter receives a sampling light and a light to be measured and combines a set of sampling light and a light to be measured having polarization planes different from each other by 90 degrees and polarization planes of 90 degrees to each other. The first calcite (19a) that outputs a total of three lights of different sampling light and measured light
And a half-wave plate (21a) that rotates the polarization states of the three lights output from this first calcite by 90 degrees, and samplings that are output from this half-wave plate and have different polarization planes of 90 degrees. The optical sampling waveform measuring device according to any one of claims 1 to 5, wherein the optical sampling waveform measuring device comprises a second calcite (19b) which combines and outputs the light and the light to be measured. 8. A pair of calcite (17a, 17b) that separates the incident first light and second light into two lights having polarization planes different from each other by 90 degrees, and one of the pair of calcite. The polarization states of two lights output from a calcite that have different polarization planes from each other by 90 degrees
A half-wave plate (21) rotated by one degree, the other calcite of the pair of calcite and the half
A pair of condensing lenses (1) that combine and condense the first light and the second light output from the wave plate, the polarization planes of which differ by 90 degrees.
8a, 18b) and a polarization separator. 9. The first light and the second light are incident, and the pair of first light and the second light having a polarization plane different from each other by 90 degrees are combined, and the polarization planes are different from each other by 90 degrees. A first calcite (19a) that outputs a total of three lights of the first light and the second light, and rotates the polarization state of the three lights output from the first calcite by 90 degrees 1/2 The wave plate (21a) and the second calcite (19b) that outputs the combined first light and second light output from the half-wave plate with mutually different polarization planes of 90 degrees. Polarization separator equipped. 10. A first beam splitter for splitting an incident first beam and a second beam into two beams having polarization planes different from each other by 90 degrees.
Of the calcite part (17a, 17b) and the first light and the second light which are different in polarization plane from each other by 90 degrees from the four lights output from the first calcite part, The second calcite part (22a, 2a that outputs to the optical path
2b) Polarization separator with. 11. A combination of a pair of first light and second light, into which first light and second light are incident and whose polarization planes differ by 90 degrees, and polarization planes differ by 90 degrees from each other. The first calcite (19a) that outputs a total of three lights of the first light and the second light, and the first light and the second light that are output from the first calcite and have mutually different polarization planes of 90 degrees. Polarization demultiplexer equipped with a second calcite (19b) that combines and outputs the light.