JPH03235922A - Optical switch - Google Patents

Abstract

PURPOSE:To eliminate polarization dependency and to improve the coupling ability with an optical fiber by using a fiber type optical amplifier to which a rare earth element with an amplification gain is added. CONSTITUTION:The effect of the transition of the fiber type optical amplifier 1 from absorption to amplification, from light transmission to amplification, or from absorption to light transmission to input wavelength is utilized. Namely, optical multiplexers 2 are interposed in three fiber type optical amplifiers 1 respectively and an exciting light source 6 is coupled with the optical multiplexers 2 through an optical distributor 5a. Exciting light in a continuous oscillation state which is emitted by the exciting light source 6 is distributed by the optical distributor 5a to the respective optical multiplexers 2 as outputs P1, P2, and P3 with time. Amplifiers formed by adding the rare earth element to optical fibers are used as the fiber type optical amplifiers 1. Consequently, there is no polarization dependency and the coupling ability with optical fibers is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to an optical switch required in the field of optical communication.

<Prior Art> In the field of optical communications, optical transmission systems using optical fibers instead of electrical signals have been put into practical use, creating the need for optical line settings, optical path switching, and the like. In particular, it is desired to switch a large number of optical fiber lines, and optical switches based on various principles have been devised and used, but they have the following drawbacks.

<1) 0/B, B10 conversion type optical switches have the potential to be large matrix type optical switches, but they have the drawback of not being able to take full advantage of the broadband nature of optical signals.

(2) Directional coupling type optical switches have polarization dependence and have problems in compatibility with optical fiber transmission lines.

(3) An optical switch using a laser amplifier has a gain,
Although it has the advantage of being able to compensate for signal loss in systems using multiplexers and demultiplexers, it has the disadvantages of polarization dependence and high coupling loss with fibers.

(4) In order to construct an optical matrix switch with a large number of inputs and outputs using the above principles, it is necessary to perform multiplexing and demultiplexing, but the matrix size increases due to losses caused by this and losses caused by elements. A separate optical amplifier was required to compensate for the limited or loss.

(5) Conventionally, in order to configure an optical matrix switch having a large number of inputs and outputs using the above principle, it is necessary to
It is composed of a combination of optical switches such as ×2.2 × 2.2 × 1, and because they are driven individually, the controllability is poor (
, because each switch must be provided with a power source, etc.
There was a drawback that the optical circuit settings could not be easily performed.

<Problem to be solved by the invention> The present invention has been made in view of the above-mentioned prior art,
A rare-earth element-doped fiber optical amplifier with no polarization dependence, good coupling with optical fibers, and amplification gain is used, and the loss during non-pumping and the gain during pumping are used to further control the In order to improve the performance, it is an object of the present invention to provide an optical switch that takes advantage of the fact that these rare earth element-doped fibers can be excited by repeated pulsed light having a time shorter than the relaxation time from the excited level.

<Means for Solving the Problems> A first configuration of the present invention to achieve the above object is to arrange a plurality of fiber type optical amplifiers doped with a rare earth element, and to pump light from the same number or less of pump light sources as the fiber type optical amplifiers. In the optical switch, the pumping light is supplied to the fiber-type optical amplifier through an optical splitter, and the pumping light is time-divided by the optical splitter and distributed as pumping pulse light to any of the fiber-type optical amplifiers. It is characterized in that the amplifier utilizes the effect that the input wavelength changes from absorption to amplification, from transparency to amplification, or from absorption to transparency.

Further, a second configuration of the present invention to achieve the above object is to arrange a plurality of fiber type optical amplifiers doped with rare earth elements, and to optically decoder coded pump light from pump light sources equal to or less than the number of the fiber type optical amplifiers. In the optical switch, the encoded pump light is decoded by the optical decoder and distributed to any of the fiber-type optical amplifiers, and the fiber-type optical amplifier absorbs and amplifies the input wavelength. It is characterized by utilizing the effect of changing from transparency to amplification or from absorption to transparency.

<Operation> Figure 1 shows the results of an experiment on the effect of a fiber-type optical amplifier excited by pulsed light on the optical signal passing through it. As shown in the inset of FIG. 1, the experimental method was as follows: Pulsed light is input from the excitation light source 03 for excitation, and signal light is passed from the signal light source 04, and the level at the receiver 05 is measured. The results shown in FIG. 1 are graphs showing the relationship between the measured receiver level and the error rate. As shown in this graph, it can be seen that when the repetition rate of the excitation pulse light is 1 KHz or more, the characteristics are almost the same as those obtained with continuous excitation light.

In other words, it is sufficient to use repetitive pulses that are shorter than the relaxation time from the excited level.

Therefore, as shown from the above results, if the configuration is such that an optical splitter can provide repeated pumping pulse light with a duration shorter than the relaxation time to multiple fiber-type optical amplifiers, by controlling the optical splitter, one pumping light source can be This makes it possible to increase or decrease the gain of multiple fiber-type optical amplifiers.

On the other hand, if the pumping light source is driven by coded pulses, and the pulsed pumping light is decoded by an optical decoder and distributed to multiple fiber-type optical amplifiers, then by controlling the pulse train that drives the pumping light source, , it becomes possible to increase or decrease the gains of a plurality of fiber-type optical amplifiers using one pumping light source.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 2 shows a first embodiment of the present invention. This embodiment relates to claim (1), and three fiber-type optical amplifiers 1 are pumped by one pumping light source 6. That is, as shown in Figure (a), three fiber type optical amplifiers 1
An optical multiplexer 2 is interposed in each of the optical multiplexers 2, and an excitation light source 6 is coupled to these optical multiplexers 2 via an optical distributor 5a.

As shown in FIG. 2(b), the continuous wave pumping light emitted from the pumping light source 6 is output by the optical distributor 5a as output P3. It is temporally branched to each optical multiplexer 2 as P2 and P3. Here, as the fiber type optical amplifier l, an optical fiber doped with a rare earth element is used. As the excitation light source 6, a laser diode is used. The optical splitter 5a is not particularly limited as long as it can output the excitation light periodically in three directions in a time-divided manner as shown in FIG. 2(b). An optical switch, a directional coupler type switch, a distributed interference type switch, etc. can be used. As mentioned above, the outputs 1, 2.3 branched by the optical splitter 5a are the same as continuous excitation light (the first ), it not only allows three fiber-type optical amplifiers 1 to be pumped simultaneously, but also has the advantage of less loss compared to a demultiplexer that splits the pumping light into three directions simultaneously. . In FIG. 2 (al), 3 is an optical isolator and 4 is an optical filter.

Next, a second embodiment of the present invention will be described with reference to FIG. This embodiment relates to claim (1), and allows the gain of each fiber type optical amplifier 1 to be controlled individually.

That is, in this embodiment, as shown in FIG. 3(a), an acousto-optic effect element 8 is used as the optical spectrometer 5a, and the other configurations are the same as in the embodiment described above. Here, as shown in FIG. 3(b), the acousto-optic effect element 8 changes the output light when different frequencies are applied. For example, frequency fl+f2. fs respectively output PitP2. Assuming that P3 corresponds, if the frequency f is periodically applied to the acousto-optic effect element 8 as shown in FIG. The gain of 1 can be controlled. Moreover, as shown in FIG. 3(d), an acousto-optic effect element 8
If frequencies f+ and fi are applied alternately and periodically to the output P
Pumping light is output alternately to + and P2, and the gains of the two fiber-type optical amplifiers 1 can be controlled.

FIG. 4 relates to a third embodiment of the present invention. This embodiment relates to claim (2), and uses the acousto-optic effect element 8 as the optical decoder 5b. That is, as shown in FIG. 4(a), a pulse train signal source 7 is connected to the excitation light source 6, and excitation pulses are transmitted from the excitation light source to the acousto-optic effect element 8.
is input. The acousto-optic effect element 8 is shown in FIG. 4(b).
As shown in the figure, frequencies f+ and fzf are given at regular intervals. Therefore, when the excitation light from the excitation light source 6 is encoded by the pulse train signal source 7 to become excitation pulse light, it is decoded by the acousto-optic effect element 8 and the output light is switched. For example, as shown in FIG. 4(C), the frequency fl+ft is applied to the acousto-optic effect element 8.
, fs are sequentially given at regular intervals and excitation pulse light is input in synchronization only with the frequency f+, then the excitation pulse light is output only to the output P. Also, the fourth
When excitation pulse light is input in synchronization with frequencies f1 and f2 as shown in the figure (d), excitation pulse light will be output for outputs P1 and P2. Furthermore, Figure 4 (
When an excitation pulse is input in synchronization with the frequency f and half of the frequency f as shown in e), the width of the output P2 becomes half the pulse width of the output P1.

In other words, the frequency f−,,,, given to the acousto-optic effect element 8 is
By changing the encoding of the pulse train signal source 7 that drives the pumping light source 6 while keeping f, , f constant, it becomes possible to select the fiber type optical amplifier 1 to be pumped.

Furthermore, in the case of a drive waveform as shown in FIG. 4(d),
In addition to selecting the fiber type optical amplifier 1 to be pumped,
Since the pulse width of the pumping pulse light applied to the fiber type optical amplifier 1 can also be changed, the fiber type optical amplifier l
By controlling the average pumping power given to the fiber-type optical amplifier 1, it is also possible to increase or decrease the gain of each fiber-type optical amplifier 1.

FIG. 5 relates to a fourth embodiment of the present invention. The present embodiment relates to claim (1), and uses a phase interference type optical decoder 5c to phase modulate pumping light to control the fiber type optical amplifier 1. That is, as shown in FIG. 5(b), the phase interference type optical decoder 5c includes a light source 9, phase change sections 10 and 11, and a phase change signal source 12°1.
The light source 9 has the same wavelength as the excitation light source 6 and is synchronized with the excitation light source 6. The outputs of the light sources 9 are each sent to a phase changer 10.11, and undergo a constant phase change under control from a phase change signal source 12.13. The phase-changed signal is input to the phase interferometric optical decoder 5c and interferes with the branched excitation signal, resulting in outputs PI and PI, respectively.
It will be output as P2.

Therefore, the excitation light source 6 driven by the pulse train signal source 7
As shown in FIG. 5(C), the phase of the phase-modulated excitation pulse light changes periodically between π and −π compared to the phase of the light source 9. Here, the phase of the signal is shown. (not signal strength), this excitation pulse is detected by the phase interferometric optical decoder 5.
When the signal is input to phase changer 10.c, it is branched to phase changer 10.c. It interferes with the light from the light source 9 whose phase has changed in II and strengthens each other,
They weaken each other. As shown in FIG. 5(C), if the phase changes by the phase changing units 10.11 are π and -π, respectively, the output P1.1 due to mutual interference. Pt
Excitation pulse lights that are inverted to each other are output. In other words, excitation pulses are alternately output to the outputs P11 and P2. As shown in FIG. 5(d), while the phase change of the phase change section 11 is constant at π, the phase change of the phase change section 10 is changed periodically, and the period of the change is If P is shifted by half a period from the excitation pulse light from the excitation light source 6, the period of the excitation pulse light of the output P becomes approximately half that of the excitation pulse light of the output P2.

In this way, by interfering and changing the phase of the pump light source, it is possible to select the fiber type optical amplifier 1 to be pumped, and furthermore, by changing the pulse width of the pump pulse light, it is possible to select the fiber type optical amplifier 1 to be pumped. It becomes possible to increase or decrease the gain of the amplifier 1.

FIG. 6 shows a fifth embodiment of the present invention. This embodiment relates to claim (2) and is a 2×3 matrix switch. That is, two input signals are each branched into one pinhole by a three-branch optical demultiplexer 14, and each is connected to an optical amplifier 15. The output of each optical amplifier 12-5 is then multiplexed into two by three optical multiplexers 17. Excitation light is branched from the acousto-optic effect element 8 to each optical amplifier 15 .

Therefore, as in the third embodiment described above, by arbitrarily controlling the six optical amplifiers 15, it is possible not only to operate as a complete matrix, but also to cut off all outputs. Become. Furthermore, if the input signal light has different wavelengths, it is possible to combine and output the same output.
It can also be used as a multiplex two-selection matrix for optical wavelength division multiplexing.

<Effects of the Invention> As explained above in detail based on the embodiments, the optical switch of the present invention uses a fiber type optical amplifier doped with a rare earth element that has amplification gain, and therefore has no polarization dependence. It has the characteristics of having good coupling properties with optical fibers. Since it uses the unexcited loss and the excited gain,
When used as an optical matrix switch (mi-wave,
Multiplexing can be performed without loss.

Furthermore, since the rare-earth element-doped fiber can be excited with repeated pulsed light having a relaxation time shorter than the excitation level, controllability is improved, such as being able to control a plurality of fiber-type optical amplifiers using as many pumping light sources.

[Brief explanation of drawings]

FIG. 1 relates to the principle of the present invention and is a graph showing the relationship between receiver level and error rate. FIG. 2 relates to the first embodiment of the present invention, and FIG. Figure (b) is a graph showing the change in waveform between each element, Figure 3 relates to the second embodiment of the present invention, figure (a) is its configuration diagram, and Figure 3) is a graph of the acousto-optic effect element. The configuration diagram, the same figure ((:) (dl is a graph showing the change in waveform between each element, respectively, FIG. 4 relates to the third embodiment of the present invention, and FIG. Figures 1 and 2) are block diagrams of the acousto-optic effect element, (C) and (d).
(e) is a graph showing the change in waveform between each element, FIG. 5 relates to the fourth embodiment of the present invention, FIG. 5(a) is its configuration diagram, and FIG. FIG. 6 is a block diagram of an optical decoder, FIGS. 6(c) and 6(d) are graphs showing changes in waveforms between each element, and FIG. 6 is a block diagram showing a fifth embodiment of the present invention. In the drawing, l is a fiber type optical amplifier, 2 is a multiplexer, 3 is an optical isolator, 4 is an optical filter, 5a is an optical spectrometer, 5b is an optical decoder, 5c is a phase interference type optical decoder, 6 is a pumping light source, 7 is a pulse train signal source, 8 is an acousto-optic effect element, 9 is a light source, 10.11 is a phase change unit, 12.13 is a phase change signal source, 14 is a waveform generator, 15 is an optical amplifier, 16 is an optical multiplexer It is. Figure 4 (a) Figure (b) p1ρ9P3 Human power diagram (C) Figure (d) Figure (e)

Claims (2)

[Claims] (1) An optical switch in which a plurality of fiber-type optical amplifiers doped with rare earth elements are arranged, and pump light from pump light sources equal to or less than the number of the fiber-type optical amplifiers is supplied to the fiber-type optical amplifiers through an optical splitter. An optical splitter divides the pumping light in time division and distributes it as pumping pulse light to any of the fiber-type optical amplifiers, and the fiber-type optical amplifier changes from absorption to amplification, from transparent to amplified, or from absorption to transparent for the input wavelength. An optical switch characterized by the use of effects. (2) In an optical switch in which a plurality of fiber-type optical amplifiers doped with rare earth elements are arranged, and coded pump light from pump light sources equal to or less than the number of fiber-type optical amplifiers is provided to the fiber-type optical amplifiers through an optical decoder, The optical decoder decodes the encoded excitation light and distributes it to any of the fiber-type optical amplifiers, and utilizes the effect that the fiber-type optical amplifier changes from absorption to amplification, from transparent to amplified, or from absorption to transparent with respect to the input wavelength. An optical switch characterized by: