JP2002280962A - Optical sn detector and method in coherent optical communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical SN detector and method in a coherent optical communication system, that can detect the SN of wavelength multiplex signal lights configured by high density, with high accuracy. SOLUTION: An optical SN detection system of a coherent optical communication, that applies wavelength multiplex to a coherent signal light, including an ASE(amplified spontaneous emission) noise light for communication, is provided with optical filters 15, 119 that transmit the coherent signal light with a prescribed channel wavelength component, a channel ASE noise detection section 114 that optically quenches the transmitted coherent signal light component to detect the signal of the channel ASE noise light component, a channel power detection section 112 that detects the signal of the channel power of the transmitted channel wavelength component, and a detection signal processing section 120 that subtracts the detection signal of the channel ASE noise optical component from the detection signal of the channel power and calculates the optical SN, on the basis of the calculation signal of the channel power of the coherent signal light and the detection signal of the channel ASE noise optical component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal-to-noise (SN) detector for a coherent optical communication system. In particular, the present invention detects the optical SN of the wavelength multiplexed signal light in the coherent optical communication system,
Optical SN of coherent optical communication to report a fault in the transmission line
The present invention relates to a detection system and method. In addition, high precision optical SN
The present invention relates to a measuring device for detection.

[0002]

2. Description of the Related Art An optical SN (signal-to-noise ratio) detector of wavelength-division multiplexed signal light disclosed in Japanese Patent Application Laid-Open No. 10-336118 is disclosed. . In recent years, developments have been made toward realizing a coherent optical communication system. In a coherent optical communication system, a wavelength division multiplexing transmission system is employed to increase transmission capacity, and a large number of signal lights are arranged within a limited wavelength band of an optical amplifier. The wavelength interval of the signal light is increased to 50 GHz or less.

On the other hand, high reliability is required for a transmission system. For example, a transmission signal is deteriorated due to an abnormality in a transmission unit on the opposite side, an optical fiber constituting an undersea transmission section, or a failure in an optical repeater. It is necessary to notify that it has not been sent. FIG. 8 is a block diagram showing a schematic configuration of an optical receiver as a premise of the present invention. Note that the same components will be denoted by the same reference numerals and symbols throughout the drawings.

As shown in FIG. 1, an optical amplifier 11 is provided on the input side of an optical receiver 10. The optical amplifier 11 inputs and amplifies a wavelength-division multiplexed signal light that has propagated through a transmission path and has been attenuated. An optical filter 15 is connected to the output side of the optical amplifier 11 via an optical coupler 12. The optical filter 15 is, for example, a bandpass filter having a full width at half maximum of 0.3 nm and a transmission wavelength λ = 1552.93 nm. All the signal lights other than the channel wavelengths, which are the 10 specific wavelengths, are blocked, and only the coherent signal light of the own channel is transmitted.

The output side of the optical filter 15 has an optical coupler 16
O / E (photoelectric) converter 18 is connected via
The / E converter 18 converts the coherent signal light into an electric signal and outputs the electric signal to a reception processing unit (not shown). The optical receiver 10 is provided with an optical SN detector as described in JP-A-10-336118. Optical SN
The preceding optical coupler 12 in the detector 20 is an optical amplifier 11
The wavelength division multiplexed signal light amplified by the above is branched, and an optical filter 13 is connected to the branch output side.

The optical filter 13 has, for example, a central wavelength λ =
It is a band filter of 1552.52 nm, and ASE (A
mplified Spontaneos Emis
Sion) Transmit the wavelength of the noise light. Optical filter 1
3 is provided with a light receiving element 14 on the output side.
Converts ASE noise light into a current signal.

On the other hand, the optical coupler 16 at the subsequent stage is an optical filter 1
The coherent signal light of the own channel transmitted through 5 is branched, and a light receiving element 17 is connected to the branch output side. The branched coherent signal light contains an ASE noise light component. The light receiving element 17
The coherent signal light of the branched channel is converted into a current signal.

[0008] The optical SN detector 20 is provided with a calculation unit 19, and the calculation unit 19 includes the light receiving element 14 and the light receiving element 17.
And converts them into voltages. The calculation unit 19 subtracts the voltage signal of the ASE noise light related to the light receiving element 14 from the voltage signal of the coherent signal light related to the light receiving element 17 to form a coherent signal light component that does not include the ASE noise light component.

Further, the arithmetic unit 19 calculates the optical SN by taking the ratio between the coherent signal light component not including the ASE noise light component and the ASE noise light component. Further, the arithmetic unit 19 monitors the calculated optical SN, and detects and reports occurrence of a failure in the transmitting unit, the optical fiber, the optical repeater, and the like from the optical SN. FIG. 9 is a block diagram showing a schematic configuration of the optical transmission unit 30 having one signal light. As shown in the figure, it is assumed that a light emitting diode (LD) 31 is provided in the optical transmission unit 30, and the light emitting diode 31 outputs a coherent signal light having a wavelength λ = 15552.93 nm.

An optical amplifier 32 is connected to the output side of the light emitting diode 31, and the optical amplifier 32 amplifies the coherent signal light from the light emitting diode 31 and outputs the amplified light to the transmission line.
The optical amplifier 32 outputs ASE noise light that is inevitably generated together with the amplified coherent signal light. FIG. 10 is a block diagram of the optical transmitter 30 of FIG. 9 to the optical receiver 1 of FIG.
It is a figure which shows the outline of the optical spectrum regarding one wave coherent signal light transmitted to 0.

As shown in FIG. 1, an optical spectrum received by the optical receiver 10 is composed of a coherent signal light component having a wavelength λ = 1552.93 nm and an ASE noise component.
In the optical filter 15 of the optical receiver 10, the channel wavelength λ
= 1552.93 nm to transmit a coherent signal light including an ASE noise component. The optical filter 13 of the optical SN detector 20 of the optical receiver 10 has a channel wavelength λ = 15
Wavelength λ = 1552.52 adjacent to 52.93 nm
nm ASE noise light is transmitted.

In this case, an ASE noise light component having a wavelength λ = 1552.93 nm and an adjacent wavelength λ = 1552.5
It is equal to the ASE noise light component of 2 nm. For this reason, by setting the center wavelength of the optical filter 13 of the optical SN detector 20 near the center wavelength of the optical filter 15, the ASE noise light obtained from the optical filter 13 is at the position of the channel wavelength of the coherent signal light. It can be approximated as ASE noise light.

FIG. 11 is a block diagram showing a schematic configuration of an optical transmitter 30 for wavelength multiplexed signal light. When the signal light has a higher density, as shown in the figure, a plurality of light emitting diodes (LD) 31-1, 31-2,
, 31-n are provided, and light emitting diodes 31-1, 3
Each of the coherent signal lights output from 1-2,..., 31-n gradually increases in wavelength from the shortest wavelength (λ = 1552.93 nm) of the light emitting diode 31-1, and the light emitting diode 31-n. It is formed to have the longest wavelength of n.

The light emitting diodes 31-1, 31-2,...
On the output side of 31-n, optical amplifiers 32-1, 32-2,
, 32-n are connected to each other, and the optical amplifiers 32-1,.
32-2,..., 32-n are light emitting diodes 31-1, 3
Amplify the coherent signal light from 1-2,..., 31-n. Also, the optical amplifiers 32-1, 32-2,.
n outputs ASE noise light together with the amplified coherent signal light.

The optical amplifiers 32-1, 32-2,..., 32-
AWG (Arrayed Wavegu) is provided on the output side of n.
(ide Grating) multiplexer 33 is connected and AW
The G multiplexer 33 removes the ASE noise light outside the signal wavelength band and multiplexes the coherent signal lights from the optical amplifiers 32-1, 32-2,..., 32-n to form a wavelength multiplexed signal light. .

The output side of the AWG multiplexer 33 has an optical amplifier 3
The optical amplifier 34 amplifies the wavelength-division multiplexed signal light formed by the AWG multiplexer 33 and outputs the amplified signal to the transmission line. The optical amplifier 34 outputs ASE noise light together with the amplified coherent signal light. FIG. 12 is a diagram schematically illustrating an optical spectrum of the wavelength-division multiplexed signal light transmitted from the optical transmission unit 30 in FIG. 11 to the optical receiver 10 in FIG.

As shown in FIG. 1, an optical spectrum received by the optical receiver 10 has a wavelength λ = 1552.
The wavelength increases stepwise from the coherent signal light component of 93 nm, and is composed of the signal light component of the longest wavelength and the ASE noise light components within and outside the band of the wavelength multiplexed signal light. The high-density wavelength-division multiplexed signal light is superimposed on adjacent signal light at the tail. Therefore, ASE noise light cannot be obtained close to each coherent signal light.

In-band and out-of-band ASE of WDM signal light
In the comparison of the noise light, out of the band of the wavelength multiplexed signal light, A
The AS outside the band of the wavelength multiplexed signal light is output by the WG multiplexer 33.
E noise light is removed, but A
SE noise light is present. On the other hand, within the band of the wavelength multiplexed signal light, the optical amplifiers 32-1, 32-2,.
There is ASE noise light due to both 2-n and the optical amplifier 34.

In the optical filter 15 of the optical receiver 10, AS
The coherent signal light of the channel wavelength including the E noise light component is transmitted. The optical filter 13 of the optical SN detector 20 of the optical receiver 10 transmits ASE noise light having a wavelength λ = 1552.52 nm, which is outside the band of the wavelength multiplexed signal light.

[0020]

In this case, an ASE noise light component having a channel wavelength λ = 1552.93 nm,
Wavelength λ = 1552.52 nm outside the band of wavelength multiplexed signal light
ASE noise light component. However, in the optical SN detector 20, the center wavelength of the optical filter 13 must be set outside the band of the wavelength multiplexed signal light.
Since the E-noise light component is low and the coherent signal light component is detected high, there is a problem that it is detected higher than the true light SN.

FIG. 13 is a diagram schematically showing another optical spectrum related to the wavelength multiplexed signal light in FIG. Since the ASE noise light components of the optical amplifiers 32-1, 32-2,..., 32-n vary, as shown in FIG. Variations occur, and ASE noise light components differ from each other.

Since the optical SN is obtained by using the ASE noise light component of the common wavelength outside the wavelength multiplex signal band, the light S of the optical receiver 10 is caused by the variation of the ASE noise light component.
There is a problem that the light SN obtained by the N detector 20 also varies. Accordingly, the present invention has been made in view of the above-described problems, and has been made in consideration of the above problems. Therefore, even in the case of a wavelength-multiplexed signal light having a high density, an optical SN communication system capable of increasing the accuracy of optical SN detection and reducing the variation in optical SN detection. An object of the present invention is to provide an SN detection device and method.

[0023]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an optical communication system for coherent optical communication in which coherent signal light including ASE noise light is wavelength-multiplexed for communication.
In the N detection system, an optical filter that transmits coherent signal light of a predetermined channel wavelength component, a channel ASE noise detector that quenches the transmitted coherent signal light component and detects a signal of a channel ASE noise light component, A channel power detector for detecting a channel power signal of a wavelength component; and a channel power signal of the coherent signal light is calculated by subtracting the detection signal of the channel ASE noise light component from the detection signal of the channel power. The calculation signal of the channel power of light and the channel A
An optical SN detection system for coherent optical communication, comprising: a detection signal processing unit that calculates an optical SN from a detection signal of an SE noise optical component.

By this means, even if the wavelength-multiplexed signal light has been increased in density, it is not necessary to add a wavelength component other than the predetermined coherent signal light component, so that it is possible to improve the accuracy of optical SN detection and reduce the variation in optical SN detection. To Preferably, a Mach-Zehnder optical modulator is provided in the channel ASE noise detector, and the Mach-Zehnder optical modulator extinguishes a coherent signal light component while leaving a channel ASE noise light component.

This means makes it possible to detect a channel ASE noise light component contained in a predetermined coherent signal light wavelength component. Preferably, the channel ASE
When a signal of the channel ASE noise light component is detected by providing a Mach-Zehnder type optical modulator in a noise detection unit, the channel ASE noise detection unit is used to compensate for a passage loss of the Mach-Zehnder type optical modulator. Side gain is set higher than that of the channel power detector.

By this means, it becomes possible to ensure the accuracy of the optical SN with respect to the passage loss of the Mach-Zehnder type optical modulator. Preferably, the detection signal processing unit is provided with a division IC having a division function, and the division IC inputs the detection signal of the channel ASE noise light component and the calculation signal of the channel power of the coherent signal light to calculate the optical SN. The optical SN detection system for coherent optical communication according to claim 1, wherein:

By this means, it is possible to calculate the optical SN without depending on the optical spectrum other than the predetermined coherent signal light wavelength component. Preferably, the optical detection system is provided in an optical receiver or an optical repeater. Can be By this means, in the optical receiver and the optical repeater, it is possible to detect an abnormality with respect to the failure of the optical transmission unit, the optical repeater, the submarine transmission section, and the optical fiber on the opposite station side.

Further, according to the present invention, there is provided an optical SN detection method for coherent optical communication in which communication is performed by wavelength-multiplexing coherent signal light including ASE noise light, wherein the step of transmitting coherent signal light of a predetermined channel wavelength component is included.
Channel A that quenches the transmitted coherent signal light component
Detecting the signal of the SE noise light component, detecting the channel power signal of the transmitted channel wavelength component, and subtracting the detection signal of the channel ASE noise light component from the detection signal of the channel power to obtain a coherent signal light. Calculating the signal of the channel power of the coherent signal light, and calculating the optical SN from the signal of calculating the channel power of the coherent signal light and the detection signal of the channel ASE noise light component. An optical SN detection method is provided.

By this means, as in the above-described invention, even if the wavelength-division multiplexed signal light is increased in density, it is not necessary to add a component other than a predetermined coherent signal light wavelength component. It enables reduction in detection variation.

[0030]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an optical receiver according to the present invention. As shown in the figure, the optical SN detector 110 is incorporated in the optical receiver 10 as an optical module, and the output side of the optical amplifier 11 and the input side of the optical filter 15 are directly connected as compared with FIG. The optical SN detection device 100 is connected to the branch output side of the optical coupler 16.

The optical SN detector 100 includes an optical SN detector 11
0 and a detection signal processing unit 120. Optical SN
The detector 110 inputs the coherent signal light branched by the optical coupler 16, branches the coherent signal light and the ASE noise light at the position of its own channel wavelength, and forms a channel power detection signal and a channel ASE noise detection signal. ,Output.

The detection signal processing unit 120 includes the optical SN detector 1
10 to channel power detection signal, channel detection A
The SE noise is input, the optical SN is calculated, and if the optical SN is abnormal, the abnormality is notified. FIG. 2 is a block diagram showing a schematic configuration of the optical SN detector 110 in FIG. As shown in the figure, an optical coupler 1 is provided on the input side of the optical SN detector 110.
The optical coupler 111 is a 3 dB coupler, receives the coherent signal light component of its own channel and the channel signal light including the ASE noise light component branched from the optical coupler 16, and branches into two.

A channel power detection unit 112 is connected to one output side of the optical coupler 111. The channel power detection unit 112 is composed of an InGaAs-PIN photodiode 113 and detects channel power including an ASE noise light component. , Channel power detection signal 117
Is output. A channel ASE noise detector 114 is connected to the other output side of the optical coupler 111, and the channel ASE noise detector 114 includes a Mach-Zehnder optical modulator 115, an InGaAs-PIN photodiode 11.
6 to detect channel ASE noise and output a channel ASE noise detection signal 118.

The Mach-Zehnder type optical modulator 115 is formed of a non-linear optical material, for example, LN (LiNbO
3) It is configured by using a waveguide type optical modulator, and has a function of electrically changing the optical path length of one of the branched waveguides and re-multiplexing. The difference in optical path length is (λ / 2) × n (λ: wavelength,
n: an odd number), when a so-called coherent light having the same phase, such as laser light, is incident on the Mach-Zehnder optical modulator 115, the coherent signal light is extinguished, and the ASE noise is reduced. Light remains.

Mach-Zehnder type optical modulator 1 used
In the example of No. 15, the passage loss was 6 dB, the half-wave voltage was 3.5 Vpp, and the optimal applied bias voltage value at which the incident coherent signal light was quenched was 1.5 V.
On the other hand, the ASE noise light amplified from the optical amplifier over a wide band is randomly generated in the amplification medium, and the phases of the waves emitted from the individual atoms and molecules are completely independent of each other.

Therefore, even if the ASE noise light enters the Mach-Zehnder type optical modulator 115 and is shifted in phase, it is attenuated by the passage loss of the Mach-Zehnder type optical modulator 115 but remains without being extinguished. FIG. 3 is a block diagram showing a schematic configuration of the detection signal processing unit 120 in FIG.

As shown in the figure, the detection signal processing unit 120
Are input to the current-voltage (IV) converters 121 and 12
2, the current-voltage conversion unit 121 receives the channel power detection signal 117 from the optical SN detector 110, converts the signal into a voltage value Pch,
Receives the channel ASE noise detection signal 118 from the optical SN detector 110 and converts it into a voltage value Pn.

Amplifiers 123 and 124 are connected to the current-voltage converters 121 and 122, respectively.
Reference numeral 124 amplifies the voltage values Pn and Pch to voltage values Pn ′ and Pch ′, respectively, with a predetermined gain. In order to compensate for the passage loss of the Mach-Zehnder optical modulator 115, the gain of the channel ASE noise detector 114 is set to be 6 dB higher than that of the channel power detector 112. This is to ensure the accuracy of the optical SN.

Further, the detection signal processing section 120 is provided with a differential circuit 125, and the differential circuit 125
The voltage values Pn 'and Pch' are input from 3, 124, and the voltage value Pch'-Pn 'of the signal light component is obtained. Further, the detection signal processing unit 120 is provided with a division IC 126. The division IC 126 inputs the voltage value Pn ′ of the channel detection ASE noise component to the numerator side, and the voltage value Pch′− of the signal light component to the denominator side. Pn 'is input, and the optical SN is obtained.

This time, as a division IC 126, a commercially available IC manufactured by Analog Devices (model number: AD534)
KD). This enables division processing.
The numerator and the denominator are opposite to the original definition of the optical SN because the quotient of the division IC operates normally in the range of 0 to 1. Furthermore, since the division IC 126 has a characteristic that the quotient is multiplied by 10 and output and is saturated at the applied voltage of 12 V,
The output voltage range of the division IC 126 is 0 to 12V.

That is, when the light SN is high, the output voltage becomes close to 0 V, and saturates to 10 V as the light SN deteriorates. Therefore, the light SN can be converted from the output voltage of the division IC 126, and the voltage of the division IC 126 is monitored.
An abnormality is notified that N has deteriorated.

Hereinafter, the case where the single coherent signal light shown in FIG. 9 is amplified by the optical amplifier 32 and the case where the wavelength multiplexed signal light shown in FIG.
, 32-2, ..., 32-n
Comparison between the present invention and the prior art shows that the optical SN and the division IC 12
The relationship with the output of No. 6 and the detection voltage will be described. FIG. 4 is a diagram showing the relationship between the optical SN and the detection voltage of the division IC 126 according to the related art.

In the prior art shown in this figure, when the optical SN is sufficiently high, the level difference of the ASE noise light can be ignored, so that the single coherent signal light shown in FIG.
2 and the wavelength multiplexed signal light shown in FIG.
After being multiplexed by the G multiplexer 33, the optical amplifiers 32-1, 32-2,
.., When the signal is amplified by 32-n
Hardly makes a difference in the detection voltages of the two. When the optical SN is deteriorated and becomes low, the level difference of the ASE noise light cannot be ignored, and the detection voltage difference becomes large.

FIG. 5 shows the optical SN and the division IC 12 according to the present invention.
6 is a diagram illustrating a relationship between detection voltages of No. 6; FIG. In the present invention shown in this figure, the case where the single-wave coherent signal light shown in FIG.
After the multiplexing by the WG multiplexer 33, the optical amplifiers 32-1, 32-2,
.., 32-n, there is almost no difference in the detection voltage of the division IC 126 in the entire range of the optical SN.

Further, regardless of the presence or absence of the AWG multiplexer 33, the relationship between the light SN and the detected voltage is the same. That is, the optical SN detection device 100 according to the present invention can correctly detect the optical SN from the detection voltage regardless of the configuration of the optical transmission unit 30. As described above, even with light of the same wavelength, by using the characteristics of ASE noise light and coherent signal light, which are incoherent light, and transmitting a predetermined signal wavelength component, the light is separated into channel power and ASE noise power. Regardless of the number of multiplexes and signal light band,
The optical SN of an arbitrary channel can be strictly calculated without depending on the optical spectrum other than the signal light wavelength.

Further, since other than the predetermined coherent signal light wavelength component is unnecessary, the outside of the signal wavelength band is
Similarly, it is possible to obtain a highly accurate light SN from the optical spectrum removed by the WG multiplexer 33. Also,
Since other than the predetermined coherent signal light wavelength component is unnecessary,
A plurality of optical amplifiers 32-1 and 32-2 of the optical transmitter 30;
,..., Even if there is variation in the ASE noise light component due to 32-n, it is possible to similarly obtain a highly accurate light SN.

Further, since the detection voltage is divided,
High-precision optical SN can be obtained without depending on optical input power. FIG. 6 is a block diagram showing a schematic configuration of the optical repeater according to the present invention. As shown in the figure, the optical repeater 40 is provided with an optical coupler 41 and an optical amplifier 42,
, 100-n are incorporated as optical modules.

The optical amplifier 42 is connected to the optical coupler 41 from the transmission line.
Amplifies the wavelength-division multiplexed signal light input via the multiplexed signal and outputs the amplified signal to the transmission line. A star coupler 43 is connected to the branch output side of the optical coupler 41, and the star coupler 43 branches the wavelength multiplexed signal light branched from the optical coupler 41 into a number of wavelength multiplexed signals. The star coupler 43 has a plurality of optical SNs corresponding to the number of wavelength multiplexes.
, 100-n are connected, and the optical SN detection devices 100-1, 100-2,.
100-n detects the optical SN and, if there is an abnormality, notifies the abnormality.

The optical SN detectors 100-1 and 100-1
Each of -2,..., 100-n includes an optical SN detector 110 and a detection signal processing unit 120, as shown in FIG. However, the configuration of the optical SN detector 110 is partially changed as described below. FIG. 7 shows the optical SN in FIG.
It is a figure which shows the schematic structure of each optical SN detector 110 of the detection apparatuses 100-1, 100-2, ..., 100-n.

As shown in the figure, an optical filter 119 is provided on the input side of the optical coupler 111 as compared with FIG. 2, and the other configuration is the same. The optical filter 119 has, for example, a full width at half maximum of 0.5. A bandpass filter having a wavelength of 3 nm and a transmission wavelength λ = channel wavelength, which blocks all signal light other than the channel wavelength and transmits only the coherent signal light of the channel. The optical SN detection device 100 shown in FIG.
, 100-n are provided as modules of the optical repeater 40, but may be used independently of the receiver 10 and the optical repeater 40. That is, even if used alone, it is effective as a measuring device for the purpose of detecting optical SN with high accuracy.

[0051]

As described above, according to the present invention,
The coherent signal light of a predetermined channel wavelength component is transmitted, the transmitted coherent signal light component is extinguished, the signal of the channel ASE noise light component is detected, the signal of the channel power of the transmitted channel wavelength component is detected, and the channel power signal is detected. The detection signal of the channel ASE noise light component is subtracted from the detection signal, the signal of the channel power of the coherent signal light is calculated, and the light SN is calculated from the calculation signal of the channel power of the coherent signal light and the detection signal of the channel ASE noise light component. Therefore, even if the wavelength-division multiplexed signal light has a high density, it is not necessary to add a component other than a predetermined coherent signal light wavelength component, so that it is possible to improve the accuracy of the optical SN detection and reduce the variation in the optical SN detection. I do.

Since the coherent signal light component transmitted by the Mach-Zehnder type optical modulator is extinguished,
It becomes possible to detect the channel ASE noise light component included in the predetermined coherent signal light wavelength component. Since the optical detection system is provided in the optical receiver or the optical repeater, even if the wavelength multiplexed signal light is increased in density, the optical transmitting unit, the optical repeater, the submarine transmission section, the optical fiber on the opposite station side It is possible to detect an abnormality with respect to the failure. Also,
The present invention is also effective for a measuring apparatus for detecting optical SN with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an optical receiver according to the present invention.

FIG. 2 is a block diagram showing a schematic configuration of an optical SN detector 110 in FIG.

FIG. 3 is a block diagram illustrating a schematic configuration of a detection signal processing unit 120 in FIG.

FIG. 4 is a diagram showing a relationship between a light SN and a detection voltage of a division IC 126 according to a conventional technique.

FIG. 5 is a diagram showing a relationship between an optical SN and a detection voltage of a division IC 126 according to the present invention.

FIG. 6 is a block diagram showing a schematic configuration of an optical repeater according to the present invention.

FIG. 7 shows optical SN detection devices 100-1 and 100 in FIG.
It is a figure which shows the schematic structure of each optical SN detector 110 of 0-2, ..., 100-n.

FIG. 8 is a block diagram showing a schematic configuration of an optical receiver as a premise of the present invention.

FIG. 9 is a block diagram illustrating a schematic configuration of an optical transmission unit 30 having one signal light.

FIG. 10 is a block diagram showing a configuration of the optical transmitter 30 shown in FIG. 9 to the optical receiver 10 shown in FIG.
FIG. 3 is a diagram schematically illustrating an optical spectrum of one coherent signal light transmitted to the optical communication device.

FIG. 11 is a block diagram illustrating a schematic configuration of an optical transmission unit 30 for wavelength multiplexed signal light.

12 is a diagram illustrating an example of a configuration from the optical transmitter 30 in FIG. 11 to the optical receiver 1 in FIG.
FIG. 3 is a diagram illustrating an outline of an optical spectrum of a wavelength division multiplexed signal light transmitted to 0;

13 is a diagram schematically illustrating another optical spectrum related to the wavelength multiplexed signal light in FIG.

[Explanation of symbols]

10 Receivers 11, 32, 32-1, 32-2, ..., 32-n, 3
4, 42 optical amplifier 15, 119 optical filter 16, 41, 111 optical coupler 18 O / E converter 30 optical transmitter 31, 31-1, 31-2, ..., 31-n light emitting diode 33 .. AWG multiplexer 40 optical repeater 43 star coupler 100, 100-1, 100-2,..., 100-n optical SN detector 110 optical SN detector 112 channel power detector 113, 116 InGaAs-PIN photodiode 114: channel ASE noise detection unit 115: Mach-Zehnder optical modulator 117: channel power detection signal 118: channel ASE noise detection signal 120: detection signal processing unit 121, 122: current-voltage conversion unit 123, 124 ... amplifier 125 ... differential circuit 126 ... division IC

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // G01J 9/00 H04B 9/00 E G01M 11/00

Claims (7)

[Claims] 1. A light S for coherent optical communication in which communication is performed by wavelength-multiplexing coherent signal light including ASE noise light.
In the N detection system, an optical filter that transmits a coherent signal light of a predetermined channel wavelength component,
A channel ASE noise detector for detecting a signal of an SE noise light component; a channel power detector for detecting a channel power signal of a transmitted channel wavelength component; and a channel A based on the channel power detection signal.
A detection signal for subtracting the detection signal of the SE noise light component, calculating a channel power signal of the coherent signal light, and calculating an optical SN from the calculation signal of the channel power of the coherent signal light and the detection signal of the channel ASE noise light component An optical SN detection system for coherent optical communication, comprising: a processing unit. 2. A Mach-Zehnder optical modulator is provided in the channel ASE noise detector, and the Mach-Zehnder optical modulator extinguishes a coherent signal light component while leaving a channel ASE noise light component. The optical SN detection system for coherent optical communication according to claim 1. 3. A channel ASE noise detecting unit comprising a Mach-Zehnder type optical modulator,
When detecting the signal of the E noise light component, the gain of the channel ASE noise detector is set higher than that of the channel power detector in order to compensate for the passage loss of the Mach-Zehnder optical modulator. The optical SN detection system for coherent optical communication according to claim 1, wherein: 4. The detection signal processing section is provided with a division IC having a division function, and the division IC is provided with the channel ASE.
The optical SN detection system for coherent optical communication according to claim 1, wherein a detection signal of the noise light component and a calculation signal of a channel power of the coherent signal light are input to calculate the optical SN. 5. The optical SN detection system for coherent optical communication according to claim 1, wherein the optical detection system is provided in an optical transceiver. 6. The optical SN detection system for coherent optical communication according to claim 1, wherein the optical detection system is provided in an optical repeater. 7. A light S for coherent optical communication in which communication is performed by wavelength-multiplexing coherent signal light including ASE noise light.
In the N detection method, a step of transmitting a coherent signal light of a predetermined channel wavelength component;
Detecting a signal of an SE noise light component; detecting a channel power signal of a transmitted channel wavelength component; and detecting the channel A from the channel power detection signal.
Subtracting the detection signal of the SE noise light component to calculate the channel power signal of the coherent signal light; and calculating the light SN from the calculation signal of the channel power of the coherent signal light and the detection signal of the channel ASE noise light component. And an optical SN detection method for coherent optical communication.