JP2001217781A - Optical wavelength division multiplex transmitter, optical wavelength division multiplex receiver, optical repeater and optical wavelength division multiplex transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical wavelength division multiplex transmitter, an optical wavelength division multiplex receiver, an optical repeater and an optical wavelength division multiplex transmission system, with which quality degradation caused by four-optical wave mixing and induced Raman scattering can be minimized, high density wavelength multiplexing is realized even in a zero distribution wavelength area and all signal light beams can be propagated in the same direction of an optical fiber transmission line in an optical wavelength division multiplex transmission system locating signal light beams over the wide range of wavelength 1450 nm-1650 nm, for example, on distributed shift fibers or non-zero distributed shift fibers. SOLUTION: This invention has a first distribution constant type optical amplifying means applied to the amplification of plural signal light beams, which are located on the side of short wavelength, including signal light beams located closely to the average zero distributed wavelengths of an optical fiber transmission line and a first centralized constant type optical amplifying means applied to the amplification of signal light beams located on the side of long wavelength except for the signal light beams close to the average zero distributed wavelengths of the optical fiber transmission line and an optical amplifying means for compensating the loss of the optical fiber transmission line is provided on both or any one of the optical wavelength division multiplex transmitter and the optical wavelength division multiplex receiver.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength division multiplex transmission apparatus, an optical wavelength division multiplex reception apparatus, an optical repeater, and an optical wavelength division multiplex transmission system. Modulated by electrical signals, multiplexed by optical passive components such as optical wavelength filters,
The optical wavelength in the optical wavelength division multiplexing technology is transmitted to an optical fiber transmission line, and the receiving side divides the wavelength-multiplexed signal light into individual wavelengths, converts them into optical signals and demodulates them into a plurality of original electrical signals. The present invention relates to a division multiplex transmitter, an optical wavelength division multiplex receiver, an optical repeater, and an optical wavelength division multiplex transmission system.

[0002]

2. Description of the Related Art In an optical wavelength division multiplexing technique, a plurality of lights having different wavelengths are modulated by a plurality of electric signals, and these are wavelength-multiplexed by an optical passive component such as an optical wavelength filter.
This is a technology that sends out to the optical fiber transmission line and separates the wavelength-multiplexed signal light for each wavelength on the receiving side, and demodulates them into a plurality of original electrical signals after photoelectrically converting them. Demultiplexing can be easily performed only by optical passive components, and is an effective technique for increasing the capacity of a transmission system.

FIG. 11 shows a configuration of a conventional optical wavelength division multiplex transmission system.

The optical wavelength division multiplex transmission system shown in FIG.
An optical transmitting apparatus 10 that modulates a plurality of lights having different wavelengths into a plurality of electric signals, multiplexes these signals and transmits the signals, and divides a plurality of wavelength-multiplexed signal lights into respective wavelengths and converts them into opto-electrical signals. Receiving device 2 for demodulating the signal into a plurality of electric signals
0, comprising one optical fiber transmission line 30 connecting the optical transmitting device 10 and the optical receiving device 20.

The optical transmitter 10 comprises a light source having a wavelength shorter than the wavelength λ0 + ΔλG, a modulator 11 for modulating the light, a multiplexer 12 for synthesizing the signal light modulated by the modulator 11, and centralized amplifiers 13 and 14. , A wavelength division multiplexing filter or an optical coupler 15, and a demultiplexer 16 for demultiplexing and outputting the signal light amplified by the receiver 17.

The optical receiver 20 includes a wavelength division filter or optical coupler 21, a centralized amplification type optical amplifier RL22, a centralized amplification type amplifier SL23, a demultiplexer 24 for demultiplexing the amplified signal light, and a wavelength longer than λ0 + λG. It comprises a modulator 26 for modulating the light source.

The transmission path 30 is an optical fiber transmission path having an average zero dispersion wavelength λ0.

Further, an optical wavelength division multiplex transmission system in which an optical repeater having an optical amplification function is arranged in the middle of an optical fiber transmission line to compensate for loss in the optical fiber transmission line is effective in terms of characteristics and cost. Widely developed.

[0009] Conventionally, a plurality of signal lights used for optical wavelength division multiplexing transmission have been erbium-doped fiber amplifiers (EDFs).
The wavelength band is often arranged at 1530 nm to 1565 nm, which is the gain band of A), but the wavelength band has been expanded in response to the recent increase in communication traffic (for example, S. Aisawa et al., “Ultra -wide band, long distance W
DM transmission demonstration ", 1998 Optical Fiber International Conference, Postdeadline Paper 11). Wavelength 1570-1
The development of a gain-shifted erbium-doped fiber amplifier for amplification around 610 nm and the development of a thulium-doped fiber amplifier for amplification around 1450-1520 nm have led to the low-loss wavelength region (<
There is a possibility that a wavelength division multiplex relay transmission system using a wavelength range of 1450 to 1650 nm, which is 0.3 dB / km 2, can be realized.

However, in order to realize a wideband optical wavelength division multiplexing transmission system as described above, especially on a dispersion-shifted fiber or a non-zero dispersion-shifted fiber, various nonlinear effects caused by the dispersion of the fiber are required. Systems must be designed to minimize the effects of

Hereinafter, a fiber nonlinear effect that can occur in a broadband wavelength division multiplexing transmission system on a dispersion-shifted fiber or a non-zero dispersion-shifted fiber will be described in detail.

First, signal light arranged in a region of the transmission line fiber including the zero-dispersion wavelength causes "four-wave mixing", whereby newly generated light becomes interference noise for the signal light. As a method for suppressing this, a method has been proposed in which the wavelengths of signal light are arranged at unequal intervals so that the wavelength of light newly generated by four-wave mixing does not match the wavelength of any signal light ( F. Forghieri et al., “Reduct
ion of Four-Wave Mixing Crosstalk in WDM Systems U
sing Unequally Spaced Channels ”, IEEE Photonics T
echnology Letters, 6, pp. 754-756, 1994).

Further, there is a method of reducing the input power of the signal light to the optical fiber by inputting the pumping light to the transmission line and giving the signal light a distributed constant Raman amplification gain, thereby reducing the generation efficiency of four-wave mixing. Proposed (N.Takachio
Et al., “32x10 Gbps distributed Raman amplification tr
ansmission with 50 GHz channel spacing in the zero
dispersion wavelenth region over 640 km of 1.55-
μm dispersion shifted fiber ”, 1999, International Conference on Optical Fiber, Postdeadline Paper 9). Distributed-constant Raman amplification provides gain to light with wavelengths several nm to 110 nm longer than the pump light wavelength. As it becomes maximum in the region of 100-110 nm long wavelength and becomes shorter than that,
Decrease gradually. This four-wave mixing also occurs between signal light arranged on the shorter wavelength side than the region including the zero-dispersion wavelength and signal light arranged on the longer wavelength side from the same region. Deterioration due to this is described in J. Kani et al.'S Bi-direction
al transmission ofr suppressinginter-wavelength-ba
nd nonlinear interactions in ultra-wide band WDM t
ransmission systems ”, IEEE Photonics Technology L
etters, vol. 11, pp. 376-378, 1999. As described above, the same paper states that deterioration caused by four-wave mixing between two regions having different wavelengths can be suppressed by transmitting the two regions bidirectionally.

In the optical wavelength division multiplexing transmission system using the wide wavelength region as described above, another possible nonlinear effect is "stimulated Raman scattering". Stimulated Raman scattering is a phenomenon in which, when two lights having different wavelengths propagate through a nonlinear medium, short-wavelength light becomes pumping light and amplifies long-wavelength light. And transmission quality is degraded. It is known that the generation efficiency of stimulated Raman scattering in a silica-based optical fiber increases as the wavelength interval between two lights increases, and reaches a maximum at about 100 nm.

A design method for minimizing quality degradation due to these nonlinear effects is described in a paper by J. Kani et al., “Inter-wavelength.
-band nonlinear interactions and their suppression
inmulti-wavelength-band WDM transmission system
s ”, IEEE Journal of Lightwave Technology, vol. 1
7, November, 1999. FIG. 12 shows a conceptual diagram of the method described here. According to this method, the signal light arranged in the region including the zero dispersion wavelength is:
They are arranged so that their wavelength intervals are unequal. Further, the signal light arranged in the region including the zero-dispersion wavelength and the signal light arranged in the region on the shorter wavelength side by this means that the signal light arranged in the region on the longer wavelength side from the region including the zero-dispersion wavelength and the transmission line fiber Is propagated in the opposite direction. That is, bidirectional transmission is performed. The paper details that this design minimizes the degradation due to the four-wave mixing among the degradation due to the non-linear effect described above.

[0016]

However, in the system shown in FIG. 12, the signal light is arranged so that the wavelengths are unequally spaced at the zero-dispersion wavelength. Transmission cannot be performed.

In addition, the bidirectional transmission used in the method has a problem that its operation may be complicated.

Further, the method has a problem that, among the above-described nonlinear effects, deterioration caused by excess loss of short-wavelength signal light due to stimulated Raman scattering cannot be avoided.

The present invention has been made in view of the above points, and has been made in consideration of the above points, and is an optical wavelength division multiplexing device that arranges signal light over a wide range such as a wavelength of 1450 nm to 1650 nm on a dispersion shifted fiber or a non-zero dispersion shifted fiber. In a multiplex transmission system, quality degradation caused by four-wave mixing and stimulated Raman scattering is minimized, high-density wavelength multiplexing is realized even in the zero-dispersion wavelength region, and all signal light is transmitted through the optical fiber transmission line. It is an object of the present invention to provide an optical wavelength division multiplexing transmission device, an optical wavelength division multiplexing reception device, an optical repeater, and an optical wavelength division multiplexing transmission system that can be propagated in the same direction.

[0020]

FIG. 1 is a block diagram showing the principle of the present invention.

The present invention (claim 1) provides an optical wavelength division multiplexing transmission system having a modulating means 110 for modulating a plurality of lights having different wavelengths by a plurality of electric signals and a means for wavelength multiplexing and transmitting the modulated signal light. An apparatus 100 that inputs pump light into an optical fiber transmission line 300 to
0 is an optical amplifying medium, and a distributed constant type optical amplifying means applied to amplify a plurality of signal lights arranged on the short wavelength side including the signal light arranged near the average zero dispersion wavelength of the optical fiber transmission line 300. An optical amplifying means 13 having lumped-constant optical amplifying means applied to amplify signal light disposed on the long wavelength side other than the vicinity of the mean zero dispersion wavelength of the optical fiber transmission line 300
Has zero.

According to the present invention (claim 2), the optical amplifying means 130
, The transmission line input power of the signal light arranged at least near the zero dispersion wavelength is set to −2 dBm or less.

According to the present invention (claim 3), a separating means 230 for separating a plurality of wavelength-multiplexed signal lights for each wavelength, and a photoelectric conversion of the separated signal lights to demodulate them into a plurality of electric signals. An optical wavelength division multiplexing receiving apparatus 200 having demodulation means 260, comprising: amplifying a plurality of signal lights arranged on a short wavelength side, including signal lights arranged near an average zero dispersion wavelength of an optical fiber transmission line 300. And a lumped-constant-type optical amplifying means applied to amplify signal light arranged on the long wavelength side other than the vicinity of the mean zero dispersion wavelength of the optical fiber transmission line 300. It has optical amplification means 240.

The present invention (claim 4) provides an optical amplifier 240
, The transmission line input power of the signal light arranged at least near the zero dispersion wavelength is set to −2 dBm or less.

According to a fifth aspect of the present invention, there is provided an optical repeater disposed in the middle of an optical fiber transmission line for compensating for a loss in the optical fiber transmission line. Distributed constant type optical amplification means applied to amplify a plurality of signal lights arranged on the short wavelength side, including a signal light arranged near an average zero dispersion wavelength of an optical fiber transmission line, using a transmission line as an optical amplification medium. And a lumped-constant-type optical amplifying unit applied to amplify signal light disposed on the long wavelength side near the average zero dispersion wavelength of the optical fiber transmission line.

According to a sixth aspect of the present invention, there is provided an optical wavelength division multiplexing transmission apparatus having a modulating means for modulating a plurality of lights having different wavelengths with a plurality of electric signals, and a means for multiplexing and transmitting the modulated signal light. Wavelength division multiplex receiving apparatus comprising: a separating unit that separates a plurality of wavelength-multiplexed signal lights for each wavelength; and a demodulating unit that performs photoelectric conversion of the separated signal light and demodulates the separated signal lights into a plurality of electric signals. An optical wavelength division multiplexing transmission system comprising: amplification of a plurality of signal lights arranged on a short wavelength side, including signal lights arranged near an average zero dispersion wavelength of an optical fiber transmission line. The first distributed constant type optical amplifying means and the first lumped constant type optical amplifying means applied to the amplification of signal light arranged on the long wavelength side other than the vicinity of the mean zero dispersion wavelength of the optical fiber transmission line include: Have optical fiber transmission line loss An optical amplification means for compensating, optical wavelength division multiplexing transmission apparatus, both the optical wavelength-division multiplexing receiving apparatus or,
Prepare for either one.

According to the present invention (claim 7), the transmission line is used as an optical amplification medium by inputting pumping light to the transmission line, and includes signal light arranged near the average zero dispersion wavelength of the optical fiber transmission line.
A second distributed constant type optical amplifying means applied to amplify a plurality of signal lights arranged on the short wavelength side, and a signal light arranged on the long wavelength side near the average zero dispersion wavelength of the optical fiber transmission line. And a second lumped-constant-type optical amplifying unit applied to the amplification.

According to the present invention (claim 8), the first and second lumped-constant type optical amplifiers are used to set the transmission line input power of the signal light arranged at least near the zero dispersion wavelength to -2 dBm or less. I do.

As described above, the present invention provides a method for controlling a dispersion-shifted fiber or a non-zero dispersion-shifted fiber,
For example, in an optical wavelength division multiplexing transmission system in which signal light is arranged over a wide range such as a wavelength of 1450 nm to 1650 nm, quality degradation caused by four-wave mixing and stimulated Raman scattering is minimized, and high quality is achieved even in the zero dispersion wavelength region. Density wavelength multiplexing can be realized, and these can be realized under the condition that all signal lights are propagated in the same direction on the optical fiber transmission line.

This is because, in the four-wave mixing in which the signal light arranged in the region including the zero-dispersion wavelength is generated, distribution amplification is applied to reduce the input power of the signal light near the zero-dispersion wavelength to the fiber transmission line at least. By reducing, the generation efficiency can be greatly reduced.

Four-wave mixing that occurs between the signal light arranged on the shorter wavelength side than the region including the zero-dispersion wavelength and the signal light arranged on the longer wavelength side than the region including the zero-dispersion wavelength occurs. By applying distributed amplification to reduce the input power to the fiber transmission line of the signal light on the short wavelength side of the same signal light, the generation efficiency can be greatly reduced.

Transmission quality degradation due to excess loss of short-wavelength signal light from long-wavelength signal light through stimulated Raman scattering is caused by excitation of distributed-constant light amplification on the short-wavelength side of signal light applied in distributed-constant amplification. By introducing light, the excess loss is reduced because it is compensated by distributed Raman amplification.

[0033]

FIG. 2 shows the relationship between the signal light wavelength of the present invention and the applied optical amplification method.

As shown in the figure, distributed constant type optical amplification by Raman amplification is applied to the amplification of a plurality of signal lights arranged near the average zero dispersion wavelength of the optical fiber and on the shorter wavelength side. Applying a lumped-constant optical amplification width to the amplification of signal light arranged on the long wavelength side from around the average zero dispersion wavelength,
At least the transmission line input power of each of the plurality of signal lights near the mean zero dispersion wavelength is set lower than the transmission line input power of each of the plurality of signal lights arranged on the long wavelength side.

In order to realize this, in some or all of the optical transmitter, the optical receiver, and the optical repeater in the wavelength division multiplexing system, the transmission path is connected to the optical amplification medium by inputting the excitation light to the transmission path. The optical amplifying device has a function of performing distributed optical amplification and a function of performing lumped-constant optical amplification by including an optical amplifying medium inside the optical amplifying device.

Here, in order to compensate for the distributed constant type amplification gain of the signal light arranged near the average zero dispersion wavelength and on the shorter wavelength side, a part of the optical transmitter, the optical receiver, the optical repeater or , A lumped-constant-type amplification may be arranged in all cases.

The term “around the mean zero dispersion wavelength” described herein indicates the region of λ0 ± ΔλG in FIG.

One of the reasons for providing a finite ΔλG is to take into account manufacturing variations in the zero dispersion wavelength of the transmission line fiber. The allowable manufacturing dispersion of the zero-dispersion wavelength is ± 25 nm as a standardized value (ITU-T G653).
Since the fiber is manufactured aiming at the center wavelength, the actual variation may be smaller than this. ΔλG is set in consideration of this variation.

Another reason for providing a finite ΔλG is that
It relates to the generation efficiency of four-wave mixing. The area where signal degradation due to four-wave mixing can occur is the zero dispersion wavelength λ0 ±
ΔλG (FWM), and ΔλG (FWM) is finite.
For example, it is described in Japanese Patent Application Laid-Open No. 7-107069 "Optical wavelength division multiplexing transmission system and optical dispersion compensation system". The document states that ΔλG (FWM) needs to be 10 nm or more as a numerical sequence when the number of channels is 16, the channel interval is 150 GHz, the transmission path input power per channel is 3 dBm, and the transmission path length is 90 km.

For the above reason, Δλ shown in FIG.
G is preferably about 10 to 35 nm. When a dispersion-shifted fiber having an average zero-dispersion wavelength of about 1550 nm is used as the transmission line fiber and ΔλG = 20 nm, the distributed constant optical amplification is arranged at a wavelength of 1570 nm or less using pump light having a wavelength of 1470 nm or less. The lumped-constant optical amplification is applied to amplification of signal light arranged at a wavelength of about 1570 nm or more.

Here, as the lumped constant type optical amplification, an erbium-doped optical fiber amplifier is used to amplify the signal light arranged in the wavelength range of about 1570 nm to 1620 nm.
A lumped-constant Raman fiber amplifier may be used for amplifying the signal light having a wavelength of 20 nm or more and 1650 nm or less.

The distributed constant amplification gain of the signal light arranged in the wavelength range and 1450 nm to 1520 nm may be compensated by lumped amplification using a thulium-doped optical fiber amplifier. Further, of the signal lights arranged in the range of about 1450 nm to 1520 nm, the distributed Raman amplification gain that becomes smaller as the wavelength becomes shorter may be supplemented by lumped amplification using a thulium-doped optical fiber amplifier.

[0043]

Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] In this embodiment, as shown in FIG. 2, the vicinity of the zero dispersion wavelength (wavelength λ0 ± ΔλG)
The distributed constant type optical amplification is applied to the signal light arranged on the short wavelength side including the above, and the lumped constant type optical amplification is applied to the signal light arranged on the other long wavelength side, as shown in FIG. In addition, the transmission line power of the signal light arranged at least near the zero-dispersion wavelength is set to be lower than the transmission line input power of the signal light arranged on the long wavelength side.

FIG. 3 shows the configuration of an optical wavelength division multiplexing transmission system according to a first embodiment of the present invention.

The system shown in FIG. 1 includes an optical transmitting apparatus 100 that modulates a plurality of lights having different wavelengths with a plurality of electric signals, multiplexes these signals, and transmits the multiplexed signal lights. And an optical receiver 200 for performing optical-to-electrical conversion and demodulating them into a plurality of electrical signals, and one optical fiber transmission line 300 connecting the optical transmitter 100 and the optical receiver 200.

Assuming that the average zero-dispersion wavelength of the optical fiber transmission line 300 is λ0, the optical transmission device 100 operates at the wavelength λ0 + ΔλG
The plurality of light sources 101 and the modulator 1 that modulates them
10, a multiplexer 120 for multiplexing the modulated signal light, a centralized optical amplifier SL130 for amplifying these, a wavelength λ0 + Δ
a plurality of light sources 102 of λG or less, a modulator 140 for modulating these, a multiplexer 150 for multiplexing the modulated signal light,
Wavelength multiplexing filter or optical coupler 1 for multiplexing signal light of wavelength λ0 + ΔλG or more and signal light of wavelength λ0 + ΔλG or less
61, an excitation light source 170 for distributed constant type amplification, a wavelength multiplexing filter or an optical coupler 162 for transmitting this excitation light to a transmission line, and a lumped amplification type optical amplifier SS180
Consists of

In the optical transmission device 100, the wavelength λ
Light sources equal to or greater than 0 + Δλ G are modulated by the modulator 110 and combined by the multiplexer 120, amplified by the centralized optical amplifier SL 130, and transmitted to the transmission line 300.

The light source having a wavelength of λ0 + ΔλG or less is
After being modulated by 40 and multiplexed by the multiplexer 150, it is transmitted to the transmission line 300. Wavelength λ0 + ΔλG
The following signal light is, for example, a lumped optical amplifier SS for compensating for a loss received inside the optical transmitter 100 after the multiplexer 150 and for compensating for a distributed constant amplification gain.
180 may be amplified.

The pumping light source 170 has a wavelength of λ0 + ΔλG for giving Raman amplification to the signal light having a wavelength of λ0 + ΔλG or less.
The excitation light source has a wavelength shorter than G by about 100 nm or more, and the excitation light source may be a combination of a plurality of excitation light sources having different wavelengths.

The optical receiver 200 includes a pump light source 220 for distributed constant amplification, a wavelength multiplexing filter 210 for transmitting the pump light source to the transmission line 300, a signal light having a wavelength of λ0 + ΔλG and a signal of λ0 + ΔλG or less. Wavelength multiplexing filter or optical coupler 23 for multiplexing the signal light of
0, a centralized optical amplifier RL240 for amplifying signal light having a wavelength of λ0 + ΔλG or more, a centralized amplifier optical amplifier RS250, and demultiplexers 260 and 270 for demultiplexing these, and receivers 280 and 290 for receiving these.

The wavelength λ0 +
The signal light longer than ΔλG is amplified by the centralized optical amplifier RL240, then split by the splitter 260 for each wavelength, and received by the receiver 280.

The signal light having a wavelength of λ0 + ΔλG or less is split by the splitter 270 for each wavelength and received by the receiver 290. The signal light having a wavelength of λ0 + ΔλG or less, for example, after the demultiplexer 270, compensates for the loss received inside the optical receiver 200, and compensates for the distributed constant amplification gain. May be amplified.

FIG. 4 shows an example of each amplification gain of the first embodiment of the present invention.

The gain-wavelength characteristic of the distributed constant type Raman amplification gain generally decreases toward the shorter wavelength side as shown in FIG. 4C, but by using a plurality of pumping light sources having different wavelengths. As shown in FIG. 2A, a relatively flat characteristic can be obtained.

As described above, the signal light arranged on the short wavelength side of the wavelength λ0 + ΔλG or less may be compensated for all the losses by the distributed constant type amplification gain as shown in FIG. As shown in FIG. 3B or FIG. 3C, the distributed constant type amplification gain may be supplemented by the lumped constant type amplifiers SS180 and RS250.

The centralized optical amplifiers SS180, RS2
The gain wavelength characteristic 50 may be substantially flat as shown in FIG. 4B to compensate for the almost flat distributed constant Raman amplification gain, or shown in FIG. 4C. like,
In order to compensate for the distributed constant Raman amplification gain that decreases as the wavelength goes to the shorter wavelength side, the gain may be higher as the wavelength goes to the shorter wavelength side.

FIG. 5 shows the input power at each signal wavelength for compensating for the distributed Raman amplification gain that becomes smaller as the wavelength becomes shorter in the first embodiment of the present invention. When the gain ratio of each amplifier is set as shown in FIG. 4C, the transmission line input power of each signal wavelength becomes larger as it goes to the shorter wavelength side at least in a region equal to or less than the average zero dispersion wavelength as shown in FIG. Will be set.

With the above-described configuration, in an optical wavelength division multiplexing transmission system in which signal light is arranged over a wide range including the zero dispersion wavelength range of the transmission line 300, high-density wavelength multiplexing is realized even in the zero dispersion wavelength region. In addition, under the condition that all the signal lights are propagated in the same direction in the optical fiber transmission line, the quality deterioration caused by four-wave mixing and stimulated Raman scattering can be minimized. The reason is as described above.

ΔλG is 10 to 35 for the above-mentioned reason.
nm, for example, 20 nm. [Second Embodiment] In this embodiment, a wavelength division multiplexing multi-relay transmission system using an optical repeater for compensating for a loss in an optical fiber transmission line will be described.

FIG. 6 shows the configuration of a wavelength division multiplexing multi-relay transmission system according to a second embodiment of the present invention. In this embodiment,
The relationship between the signal light wavelength and the applied optical amplification method is the same as in the first embodiment described above, and is as shown in the conceptual diagram of FIG. 2 or FIG.

The optical transmitter 1 in the system shown in FIG.
The optical receiver 200 has, for example, the same configuration as that of the first embodiment. The relay device 400 is a relay device 4
00, a pump light source 401 for distributed constant amplification in the transmission line 300, a wavelength multiplexing filter for transmitting the pump light to the transmission line 300, an optical circulator or an optical coupler 410, and a signal light longer than the wavelength λ0 + ΔλG. A wavelength separating filter or an optical coupler 420 for separating signal light of wavelength λ0 + ΔλG or less, a centralized optical amplifier L430 for amplifying signal light longer than wavelength λ0 + ΔλG, a wavelength λ
A wavelength multiplexing filter or optical coupler 44 for multiplexing a signal light longer than 0 + ΔλG and a signal light having a wavelength of λ0 + ΔλG or less.
0, an excitation light source 402 for distributed constant amplification in the transmission line 300 at the subsequent stage of the relay device 400, a wavelength multiplexing filter for transmitting the excitation light to the transmission line 300, or
It comprises an optical coupler 450.

In the relay device 400, the wavelength λ0 +
The signal light longer than ΔλG is separated by a wavelength separation filter or an optical coupler 420 and the lumped optical amplifier L43
After being amplified by 0, it is multiplexed again with light of another wavelength by the multiplexer, and transmitted to the next optical fiber transmission line 300.

The signal light having a wavelength of λ0 + ΔλG or less is separated by a wavelength separation filter or an optical coupler.
The light is again multiplexed with light of another wavelength by a wavelength multiplexing filter or an optical coupler, and then transmitted to the optical fiber transmission line 300. Here, the signal light of λ0 + ΔλG or less is used, for example, to compensate for a loss received inside the optical repeater 400 after the wavelength separation filter or the optical coupler 420 and to compensate for a distributed constant type amplification gain. , May be amplified by the centralized optical amplifier S460.

The ratio of each optical amplification gain is, for example, as shown in FIG. 4, as in the first embodiment.

The configuration shown in FIG. 6 minimizes the quality deterioration caused by four-wave mixing and stimulated Raman scattering in an optical wavelength division multiplexing multi-repeater transmission system in which signal light is arranged over a wide range including the zero dispersion wavelength range of the transmission line. To achieve high-density wavelength multiplexing even in the zero-dispersion wavelength region, and to realize these under the condition that all signal lights are propagated in the same direction on the optical fiber transmission line. be able to. [Third Embodiment] In this embodiment, an example will be described in which an optical wavelength multiplex transmission system uses a dispersion-shifted fiber having an average zero dispersion wavelength of about 1550 nm as an optical fiber transmission line. In this embodiment, in the optical wavelength division multiplexing transmission systems shown in the first and second embodiments, a dispersion-shifted fiber having an average dispersion wavelength of about 1550 nm is used as an optical fiber transmission line. FIG. 7 shows the relationship between the signal light wavelength and the applied optical amplification method according to the third embodiment of the present invention. As shown in the figure, distributed signal type optical amplification is applied to the amplification of the signal light arranged in the wavelength region of about 1570 nm or less, and the amplification of the signal light arranged in the wavelength region of about 1570 nm or more includes: Lumped constant optical amplification is applied. Wavelength 1570
In order to amplify the signal light of nm or less by distributed constant amplification using Raman amplification, pump light is arranged in a wavelength region of 1470 nm or less.
The excitation light source may be a combination of a plurality of excitation light sources having different wavelengths.

In this embodiment, the signal light has, for example, a wavelength
It is arranged in the region from 1470 nm to 1650 nm.

FIG. 8 shows the configuration of an optical wavelength division multiplexing transmission system according to a third embodiment of the present invention.

As shown in the figure, in the optical transmission device 100, a plurality of light sources having a wavelength of 1570 nm or more are modulated by the modulator 121 and multiplexed by the multiplexer 131, and then amplified by the centralized optical amplifier L113. Is transmitted to the transmission path 300.

Among the light sources having a wavelength of 1570 nm or less, for example, a light source having a wavelength of 1520 nm or more is modulated by the modulator 121 and multiplexed by the multiplexer 131,
Sent to 0. The signal light having a wavelength of 1520 nm or more and 1570 nm or less, for example, after the multiplexer 131,
It may be amplified by the lumped optical amplifier M111 in order to compensate for the loss received inside 0 and to compensate for the distributed gain.

Of the light sources having a wavelength of 1570 nm or less, for example, a light source having a wavelength of 1520 nm or less is modulated by a modulator, multiplexed by a multiplexer, and transmitted to the transmission line 300. The signal light having a wavelength of 1520 nm or less is, for example, a multiplexer 131
After that, the signal may be amplified by the lumped optical amplifier S112 to compensate for the loss received inside the optical transmission device 100 and to compensate for the distributed constant amplification gain.

The gain wavelength characteristic of the lumped optical amplifier S112 may be such that the gain becomes higher toward the shorter wavelength side in such a manner as to compensate for the distributed constant type Raman amplification gain that decreases as the wavelength decreases toward the shorter wavelength side.

Similarly, as shown in FIG. 8, in the optical repeater 400, a plurality of signal lights having a wavelength of 1570 nm or more are separated by a wavelength separation filter or an optical coupler, and then separated by a centralized optical amplifier L473. Amplified
After being multiplexed with another signal light again by a wavelength multiplexing filter or an optical coupler, it is transmitted to the next transmission line 300.

Of the plurality of signal lights having a wavelength of 1570 nm or less, for example, a plurality of signal lights having a wavelength of 1520 nm or less are separated by a wavelength separation filter or an optical coupler as shown in FIG. After being multiplexed again with another signal light by the optical coupler, it is transmitted to the next transmission line 300. Here, in order to compensate for the loss received inside the optical receiving device 200 and to compensate for the distributed constant amplification gain, the signal light is transmitted by, for example, a centralized optical amplifier S472 in front of a demultiplexer. It may be amplified.

As shown in FIG. 8, of a plurality of signal lights having a wavelength of 1570 nm or less, for example, a plurality of signal lights having a wavelength of 1520 nm or more are separated by a wavelength separation filter or an optical coupler, and then, combined with a wavelength multiplexing filter. Alternatively, after being multiplexed again with another signal light by the optical coupler, it is then transmitted to the transmission line 300. Here, the signal light is transmitted to the optical receiver 20.
To compensate for the loss received inside 0 and to compensate for the distributed gain, for example, it may be amplified by a lumped optical amplifier M471 in front of a demultiplexer. further,
In the optical receiver 200, a plurality of signal lights having a wavelength of 1570 nm or more are separated by a wavelength separation filter or an optical coupler, and amplified by a centralized optical amplifier L243.
After being demultiplexed for each wavelength by the demultiplexer 263, it is received by the receiver 283.

Among the plurality of signal lights having a wavelength of 1570 nm or less, for example, a plurality of signal lights having a wavelength of 1520 nm or less are separated by a wavelength separation filter or an optical coupler as shown in FIG. After each splitting,
Received by receiver 282. Here, in order to compensate for the loss received inside the optical receiving device 200 and to compensate for the distributed gain, for example, the signal light is lumped to a centralized optical amplifier S 242 before the splitter 262. May be amplified.

Of the plurality of signal lights having a wavelength of 1570 nm or less, for example, a plurality of signal lights having a wavelength of 1520 nm or more are separated by a wavelength separation filter or an optical coupler as shown in FIG. , And is received by the receiver 282. Here, the signal light is used to compensate for the loss received inside the optical receiving device 200 and to compensate for the distributed constant amplification gain.
For example, a centralized optical amplifier M241 is provided at a stage before the duplexer 261.
May be amplified.

The centralized optical amplifier S242 may be, for example, a thulium-doped optical amplifier that provides a gain in a wavelength region of about 1450 nm to 1520 nm, or may provide a gain in an arbitrary wavelength region by selecting a pump light wavelength. May be a lumped-constant-type Raman amplifier, or a combination thereof. The centralized optical amplifier M241 may be, for example, an erbium-doped optical amplifier that provides a gain in a wavelength region of about 1530 nm to 1570 nm, or a concentrated optical amplifier that can provide a gain in an arbitrary wavelength region by selecting a pumping light wavelength. It may be a constant type Raman amplifier,
A combination of these may be used. Centralized optical amplifier L
243 may be, for example, a gain-shift type erbium-doped optical amplifier that provides a gain in a wavelength region of about 1570 nm to 1610 nm, or a concentrated light that can provide a gain in an arbitrary wavelength region by selecting a pump light wavelength. It may be a constant Raman amplifier or a combination thereof.

FIG. 9 shows an example of each amplification gain in the third embodiment of the present invention.

For signal light having a wavelength of 1570 nm or longer, 100% lumped-constant type optical amplification is applied. Of the signal light arranged at a wavelength of 1570 nm or more, for example, 1570 nm to 16190 n
An erbium-doped optical amplifier is applied to the signal light arranged at m, and a lumped-constant Raman amplifier is applied to the signal light arranged at 1610 to 1650 nm. Distributed signal Raman amplification is applied to signal light arranged at a wavelength of 1570 nm or less. Among them, a larger lumped-constant-type amplification gain is given to a shorter wavelength side signal light in order to compensate for a distributed constant-type Raman gain that decreases as the wavelength becomes shorter.
For example, using a thulium-doped optical amplifier, a lumped-constant-type amplification gain is provided on the shorter wavelength side to signal light arranged at a wavelength of 1470 nm to 1520 nm. By the above, in the optical wavelength division multiplexing transmission system and the multi-repeater transmission system in which signal light is arranged over a wide wavelength range using the dispersion system fiber, four-wave mixing, while minimizing the quality degradation caused by stimulated Raman scattering, High-density wavelength multiplexing can be realized even in the zero-dispersion wavelength region, and these can be realized under the condition that all signal lights are propagated in the same direction on the optical fiber transmission line.

FIG. 10 shows the relationship between signal input power per channel and sensitivity degradation in the zero dispersion wavelength band and the non-zero dispersion wavelength band of the present invention.

This figure shows the signal reception sensitivity degradation (experimental value) with respect to the fiber input power per channel when the wavelength multiplexed signal light of eight channels of 200 GHz propagates through the dispersion shift fiber of 40 km.

The zero-dispersion wavelength of the dispersion-shifted fiber used is about 1552 nm, and the results for signal light arranged in the zero-dispersion wavelength band centered at the wavelength of 1552 nm are indicated by black circles and the wavelength is 1585 nm.
Triangles indicate the results for signal light arranged in a non-zero dispersion wavelength band centered at nm.

As can be seen from the figure, when the input power is increased with respect to the signal light arranged in the zero-dispersion wavelength band, four-wave mixing causes severe deterioration (in this case, the deterioration is caused by four-wave mixing). One thing is that M. Jinno et al., “First demonstration of 1580 nm wavelength band WD
M transmission ”, Electron. Lett., Vol. 33, pp. 882
-883).

As shown in the figure, the fiber input power of the signal light arranged near the zero dispersion wavelength in the present invention is, for example,
It can be seen that setting to -2 dBm or less is effective (the lower the better, the better, -4 dBm or less, -6 dB
m or -8 dBm or less).

The present invention is not limited to the above embodiment, but can be variously modified and applied within the scope of the claims.

[0087]

As described above, according to the present invention, optical wavelength division multiplexing transmission for arranging signal light over a wide range, for example, 1450 nm to 1650 nm, on a dispersion-shifted fiber or a non-zero dispersion-shifted fiber. In the system, quality degradation caused by four-wave mixing and stimulated Raman scattering is minimized, high-density wavelength multiplexing is realized even in the zero-dispersion wavelength region, and all signal lights are transmitted to the same optical fiber transmission line. Direction.

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a diagram showing the relationship between the signal light wavelength of the present invention and the applied optical amplification method.

FIG. 3 is a configuration diagram of an optical wavelength division multiplexing transmission system according to a first example of the present invention.

FIG. 4 shows zero of each amplification gain in the first embodiment of the present invention.

FIG. 5 is a diagram showing input power at each signal wavelength for compensating for a distributed Raman amplification gain that becomes smaller on a shorter wavelength side according to the first embodiment of the present invention.

FIG. 6 is a configuration diagram of a wavelength division multiplexing multi-relay transmission system according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a relationship between a signal light wavelength and an applied optical amplification method according to a third embodiment of the present invention.

FIG. 8 is a configuration diagram of an optical wavelength division multiplexing transmission system according to a third embodiment of the present invention.

FIG. 9 is an example of each amplification gain of the third embodiment of the present invention.

FIG. 10 is a diagram illustrating a relationship between signal input power per channel and sensitivity degradation in a zero dispersion wavelength band and a non-zero dispersion wavelength band according to the present invention.

FIG. 11 is a conceptual diagram of a conventional ultra-wideband optical wavelength multiplex transmission system including a zero dispersion wavelength region.

FIG. 12 is a configuration diagram of a conventional optical wavelength division multiplex transmission system.

[Explanation of symbols]

REFERENCE SIGNS LIST 100 Optical transmission device 101 Light source having wavelength longer than λ0 + ΔλG 102 Light source having wavelength shorter than λ0 + ΔλG 110 Modulating means, modulator 111 Optical amplifier M 112 Optical amplifier S 113 Optical amplifier L 120 Multiplexer 121 Modulator 130 Optical amplifying means, concentrated Amplifying optical amplifier SL 131 Multiplexer 140 Modulator 150 Multiplexer 161 Wavelength multiplexing filter or optical coupler 162 Wavelength multiplexing filter or optical coupler 170 Amplifies signal light arranged in a wavelength region shorter than λ0 + ΔλG by distributed constant type. Light source for distributed light 171 Pump light source for distributed constant optical amplification 180 Centralized amplification type optical amplifier SS 200 Optical receiver 210 Circulator or wavelength multiplexing filter 220 Separating means, Distributed light of distributed wavelength type shorter than λ0 + ΔλG Excitation light source for amplification 221 Distribution constant Excitation light source for optical amplification 230 Wavelength separation filter or optical coupler 240 Optical amplification means, Centralized amplification type optical amplifier RL 241 Optical amplifier M 242 Optical amplifier S 243 Optical amplifier L 250 Demodulation means, Centralized amplification type optical amplifier RS 260, 270 min Wavers 261, 262, 263 Demultiplexers 280, 290 Receivers 281, 282, 283 Receiver 300 Optical fiber transmission line with average zero dispersion wavelength λ0 400 Optical repeater 401 Excitation light source 402 Distributed excitation light source for optical amplification 403 Excitation light source 410 for distributed constant type optical amplification 410 circulator or wavelength multiplexing filter 420 wavelength separation filter 430 centralized amplification type optical amplifier L 440 wavelength multiplexed filter or optical coupler 450 circulator or wavelength multiplexed filter 460 centralized amplification type optical amplifier S 471 light Amplifier M 472 Amplifier S 473 optical amplifiers L

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04J 14/00 14/02 (72) Inventor Koji Masuda 2-3-1 Otemachi, Chiyoda-ku, Tokyo Date F-term (reference) in this telegraph and telephone company 5F072 AB09 AK06 JJ20 KK11 KK15 MM03 MM07 QQ04 QQ07 YY17 5K002 AA01 AA03 AA06 BA04 BA05 CA01 CA13 DA02 FA01

Claims (8)

[Claims] 1. An optical wavelength division multiplexing transmission apparatus comprising: means for modulating a plurality of lights having different wavelengths by a plurality of electric signals; and means for multiplexing and transmitting the modulated signal light. Applying pumping light to the transmission line as an optical amplifying medium, applied to the amplification of multiple signal lights arranged on the short wavelength side, including signal light arranged near the average zero dispersion wavelength of the optical fiber transmission line And a lumped-constant-type optical amplifying unit applied to amplify signal light arranged on a long wavelength side other than the vicinity of the mean zero dispersion wavelength of the optical fiber transmission line. An optical wavelength division multiplexing transmission device comprising: 2. The optical wavelength division multiplexing transmission apparatus according to claim 1, wherein the transmission line input power of the signal light arranged at least near the zero dispersion wavelength is set to −2 dBm or less by using the optical amplification means. 3. An optical wavelength division unit comprising: a separating unit that separates a plurality of wavelength-multiplexed signal lights for each wavelength; and a demodulating unit that performs photoelectric conversion of the separated signal light and demodulates the separated signal lights into a plurality of electric signals. A multiplex receiving apparatus, including a signal light disposed near an average zero dispersion wavelength of the optical fiber transmission line, and a distributed constant type optical amplification means applied to amplify a plurality of signal lights disposed on a short wavelength side; A light amplifying unit having a lumped-constant type optical amplifying unit applied to amplification of signal light disposed on a long wavelength side other than around the average zero dispersion wavelength of the optical fiber transmission line. Wavelength division multiplex receiver. 4. The optical wavelength division multiplexing receiver according to claim 3, wherein the optical amplifier means is used to set the transmission line input power of the signal light arranged at least near the zero dispersion wavelength to -2 dBm or less. 5. An optical repeater disposed in the middle of an optical fiber transmission line for compensating for a loss in the optical fiber transmission line. Amplifying medium, including signal light arranged near the average zero dispersion wavelength of the optical fiber transmission line, distributed constant type optical amplification means applied to amplification of a plurality of signal lights arranged on the short wavelength side, An optical repeater comprising lumped-constant-type optical amplifying means applied to amplify signal light disposed on a long wavelength side near an average zero dispersion wavelength of an optical fiber transmission line. 6. An optical wavelength division multiplexing transmission device having means for modulating a plurality of lights having different wavelengths with a plurality of electric signals and means for multiplexing and transmitting the modulated signal light,
An optical wavelength division multiplexing receiver comprising: a separating unit that separates a plurality of wavelength-multiplexed signal lights for each wavelength; and a demodulating unit that performs photoelectric conversion on the separated signal light and demodulates the separated signal lights into a plurality of electric signals. Wavelength division multiplexing transmission system, comprising: a first signal applied to amplify a plurality of signal lights arranged on a short wavelength side, including a signal light arranged near an average zero dispersion wavelength of an optical fiber transmission line. And a first lumped-constant-type optical amplifying means applied to the amplification of signal light arranged on a long wavelength side other than the vicinity of the mean zero dispersion wavelength of the optical fiber transmission line. An optical wavelength division multiplexing transmission system comprising: an optical amplification unit that compensates for a loss in an optical fiber transmission line; and / or both of the optical wavelength division multiplexing transmission device and the optical wavelength division multiplexing reception device. . 7. A transmission line is used as an optical amplifying medium by inputting pumping light to an optical fiber transmission line, and is arranged on a short wavelength side including signal light arranged near an average zero dispersion wavelength of the optical fiber transmission line. A second distributed constant type optical amplifying means applied to the amplification of the plurality of signal lights obtained, and applied to the amplification of the signal lights arranged near the long wavelength side near the average zero dispersion wavelength of the optical fiber transmission line. 7. The optical wavelength division multiplexing transmission system according to claim 6, further comprising an optical repeater having a second lumped constant type optical amplifying means. 8. Using the first lumped-constant-type optical amplifying unit and the second lumped-constant-type optical amplifying unit, reduce at least the transmission-line input power of signal light arranged near the zero-dispersion wavelength.
The optical wavelength division multiplexing transmission system according to claim 6 or 7, wherein the optical wavelength division multiplex transmission system is set to -2 dBm or less.