JP2581012B2 - Optical communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication apparatus for performing communication by using an optical signal obtained by multiplexing light beams each having a unique wavelength. For example, the present invention relates to an optical communication apparatus effective against a line abnormality.

[0002]

2. Description of the Related Art An optical fiber used for optical communication has a characteristic that a signal transmission band is wide. In order to make effective use of this feature, in the field of optical communication, it is common practice to multiplex a plurality of optical signals having different wavelengths onto one optical fiber and transmit the multiplexed optical signals. Such a communication system is called a wavelength division multiplexing optical communication system or a frequency division multiplexing (FDM).
This is called an optical communication system.

According to this communication method, a large amount of information can be transmitted at one time by one optical fiber.
Nowadays, demands for large-capacity optical communication are increasing, and even if the transmission band of the optical fiber is wide, the wavelength interval of the multiplexed optical signal must be narrowed. Therefore, Japanese Patent Laid-Open Publication No. Sho 62-122344 proposes various transmission systems that can sufficiently demodulate a signal even if the wavelength interval is small.

By the way, in an optical communication system in which a large number of signal lights are transmitted at one time due to multiplexing, the configuration of the optical communication device becomes complicated and the number of components increases. If even some of the components fail, a circuit abnormality may occur in which a signal cannot be extracted from light of a certain wavelength. In particular, in the highly computerized modern age, since some of these line abnormalities cause the entire system to stop, it is important to provide a redundant configuration for the communication device. Therefore, conventionally, a standby communication device is prepared separately from the current communication device, and when an abnormality occurs, the line is switched to the standby communication device to ensure communication reliability.

FIG. 2 shows an example of such a conventional frequency division multiplexing optical communication device. First, the configuration on the transmitting side will be described. ,..., 13 to which the signal lights λ ₁ , λ ₂ , λ _n having different wavelengths are input, respectively, are connected to the optical switch 14. Have been.

FIG. 3 shows such signal lights λ ₁ , λ ₂ , λ _n.
FIG. Optical switching device 1 shown in FIG.
The optical fiber 1 includes first, second,..., And n-th optical fibers 1.
Each of the optical signals input from 1, 12,..., 13 is switched to one of two output destinations. That is, the optical switch 15 sends an optical signal input from the optical fiber 11 to the optical fiber 18 or 19, the optical switch 16 sends an optical signal input from the optical fiber 12 to the optical fiber 20 or 21, and the optical switch 17 Is the optical fiber 1
The optical signal input from 3 is switched to 22 or 23. The output side of the optical switching device 14 is connected to two systems of optical transmitters 24 and 25 for multiplexing the signal light input through n optical fibers. The optical transmitter 24 is a working system, and the optical transmitter 25 is a standby system. The outputs of these optical transmitters 24 and 25 are respectively connected to optical fibers 26 and 2.
7, and is input to the optical switch 28. The optical switch 28 selects one of them and sends it to the working optical fiber 29 or the standby optical fiber 30.

Next, the configuration of the receiving side will be described. On the receiving side, the optical fibers 29, 30 of each system are connected to the corresponding optical receiving units 31, 32. In the active optical receiving unit 31, the optical distributor 29 is connected to the optical fiber 29.
3 are connected and distribute these to n multiplexed optical signals. The distributed n optical signals 34, 35, ..., 3
Reference numeral 6 denotes n optical band-pass filters 38, 39,..., 40 for extracting light having specific wavelengths of λ ₁ , λ ₂ , and λ _n , respectively.
Is input to The light having the unique wavelengths of λ ₁ , λ ₂ , and λ _n obtained as described above is input to the light receiving units 45, 46,... Optical receiver 45, 4
,..., 47 and the light whose signal level has been adjusted are transmitted to the corresponding n optical fibers 48, 49,.
Sent to 0. These optical fibers 48, 49, ...
, 50 are connected to an optical switching device 69. The optical fibers 48, 49,..., 50 are input to the corresponding ones of the optical switches 70, 71,.
One of the lights input from 6, 67,..., 68 is selected. The light of each of these selected wavelengths is sent to a subsequent device (not shown) via a corresponding one of the n optical fibers 73, 74,..., 75.

Since the configuration of the standby optical receiving unit 32 is the same as that of the working optical receiving unit 31, the description of that part is omitted.

In such an optical communication apparatus, signal light having unique wavelengths λ ₁ , λ ₂ ,..., Λ _n is input to each of n optical fibers 11, 12,. You. The optical switching device 14 normally selects the active system, and transmits the optical transmitter 24 via the optical fibers 18, 20,.
These signal lights are input to the. The optical transmitter 24 multiplexes these signal lights and sends them to the optical fiber 26. If any abnormality occurs in this system, signal light processing via the optical transmitter 25 is performed.

The multiplexed signal light transmitted from the optical fiber 26 or the optical fiber 27 is selected by the optical switch 28, and is usually transmitted to the working optical receiving unit 31 via the optical fiber 29. You. In the optical receiving unit 31, these signal lights are distributed to n lines by the optical distributor 33, and the n optical band-pass filters 38, 39,.
Respectively, and the corresponding signal light is extracted. These extracted signal lights are transmitted to the optical receivers 45 and 46,
, 47 and the optical fibers 48, 49,..., 50 reach the optical switching device 69, from which they are sent to the corresponding ones of the n optical fibers 73, 74,. Will be. Standby optical receiving unit 32
The description of the operation is omitted.

As described above, the conventional optical communication apparatus is provided with a transmitter and a receiver having exactly the same configuration consisting of two systems, a working system and a protection system. For example, when an abnormality occurs in the working system, an optical switch is used. By switching the transmission path of the optical signal to a spare device, optical communication is enabled even when a line abnormality occurs.

[0012]

However, in such an optical communication device, an abnormality of the device is detected by the optical receiving units 31, 32.
Occur relatively often. It is for the following reasons.
First, the transmitter multiplexes the signal light of each wavelength. Even if the number of signal lights to be processed is increased, a similar signal processing portion is simply added. That is, the configuration of the transmitter is simpler than that of the receiver, and there are few cases where signal light of a specific wavelength to be transmitted is lost. Also, there is no case where only a specific wavelength is not transmitted in the middle of an optical fiber which is a transmission path of an optical signal. However, on the receiver side, a filter and many other circuit devices are required to extract a target signal light from the multiplexed signal light. For this reason, the probability of failure as a whole increases, and a relatively large number of cases in which signal light of some wavelengths cannot be extracted occur. Of course, considerable reliability can be ensured by duplicating the communication system as shown in FIG. 2, but it has been desired to further increase the reliability as the importance to optical communication increases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical communication device capable of taking measures against a failure in the system itself when a failure occurs on the receiving side for receiving the multiplexed signal light.

[0014]

According to the first aspect of the present invention, (a) light having a unique wavelength is frequency-divided.
And the number of multiplexed signal lights is greater than that of the n systems.
An optical distributor for distributing the number of signal lights, and (b) the optical distributor
Of n signal light components distributed by
Extract the signal light of the corresponding system wavelength for
(C) optical bands for these n systems
Each system has its own unique
An optical receiver for each system that individually receives signal light of a wavelength,
(D) One of these system-specific optical receivers receives signal light.
When an error occurs in the signal, the wavelength of the signal light in which the error occurred
Local oscillation that outputs light of the same wavelength as local oscillation light
A light source and (e) an optical bandpass filter for n systems from the optical distributor.
Signal light other than that distributed to the
The wavefront of the local oscillation wave output from the
The synchronization signal to be output to the local oscillation light source
Abnormal signal output from the local oscillation light source due to
Optical heterodyne reception to extract signal light of the same wavelength as light
And (f) output from each system optical receiver
Input the signal light and the signal light output from the optical receiver,
For the signal light of the system where the normal occurs, this is
Light that switches and outputs the signal light input from the receiver
A switching device is provided in the optical communication device.

That is, according to the first aspect of the present invention, the signal light obtained by multiplexing each unique signal light is transmitted to these signal systems.
Distributed in a number greater than n, of which n
In each case, the signal light is extracted by an optical band-pass filter.
Then, each of them is received by the optical receiver. Receiving signal light
If there is an abnormality in the local oscillation light source,
Outputs light of the same wavelength as the generated signal light and distributes it.
Using the remaining signal light
It is extracted by the heterodyne receiver. At this time, the local oscillation light
The oscillation of the local oscillation light output from the
A predetermined signal light cannot be obtained because of the dam. There
In the present invention, a local wave output from a distributed wave and a local oscillation light source is used.
A synchronization signal that matches the wavefront of the oscillation wave is output to the local oscillation light source.
I try to force. The signal light obtained in this way
Is input to the optical switching device together with the signal light of each system,
Optical heterodyne receiver
Will be switched to the signal light input from
You.

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

FIG. 1 shows the configuration of an optical communication apparatus according to one embodiment of the present invention. First, the configuration on the transmitting side will be described. The same parts as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. Signal light λ ₁ , λ with different wavelengths
_2, first, second to lambda _n is inputted, ..., n-th
, 13 are connected to the optical switch 14. The optical switching device 14 includes corresponding optical switches 15, 16,..., 17, and the first, second,..., N-th optical fibers 11, 12,.
The optical signal input from 13 is switched to one of two output destinations (however, the standby system is not necessarily required in the present invention, and is not shown). The output side of the optical switching device 14 is connected to an optical transmitter 24 that multiplexes the signal light input through n optical fibers. The output of the optical transmitter 24 is input to the optical switch 28 via the optical fiber 26.

Next, the configuration of the receiver will be described. In the optical receiving unit 81, the optical fiber 29 is connected to the optical distributor. The optical distributor 82 distributes more input signal lights than the number (n) of multiplexed signal lights. The figure shows 1
The number of distributions depends on how much redundancy is to be increased, and is not limited to this. Of the light distributed by the optical distributor 82, the signal lights 34, 35,.
, 36 are the corresponding optical bandpass filters 38,
39,..., 40. On the other hand, the signal light 83 allocated extra is input to the optical receiver 84. The signal lights 41, 4 of the specific wavelengths λ ₁ , λ ₂ , λ _n extracted by the optical band-pass filters 38, 39,.
2 and 43 are input to the optical receiving units 86, 87 and 88. .., 50 and the optical switching device 69, and the n optical fibers 73, 74,.
, 75 are sent to the corresponding ones.

By the way, the optical receiving unit 8 of this embodiment
In 1, a local oscillation light source 89 is prepared in case one of the optical receiving units 85 cannot receive a predetermined optical signal. Signal lines 90, 91, and 92 for transmitting a light emission control signal for driving the local oscillation light source 89 are drawn from the respective light receiving units 86, 87, and 88 of the light receiving unit 85, and are output from the local oscillation light source 89. It is connected to the. As described above, the optical receiving unit 85 outputs the signal light and also detects the abnormality of the light extracted by the optical band-pass filter 37. Local oscillation light 9 output from local oscillation light source 89
3 is input to the optical receiver 84. The light receiving unit 84 is provided with a band-pass filter that allows light of specific wavelengths λ ₁ , λ ₂ ,..., Λ _n to pass. A synchronization signal 95 for synchronizing the signal light 83 and the local oscillation light 93 is input to the local oscillation light source 89 from the optical receiver 84. When light of a predetermined wavelength is extracted in synchronization, the extracted light 96 is output to the optical switching device 69.

The operation of the optical communication device will be described below. The frequency-division-multiplexed optical signal is input from the optical fiber 29 to the optical distributor 82 of the optical receiving unit 81. The optical distributor 82 further outputs a signal light 83 in addition to the n signal lights 34, 35,... Among them, n signal lights 3
.., 36 are optical bandpass filters 3 respectively.
Is input to _{8,39,40, λ 1, λ 2,} ......, each lambda _n specific wavelengths of light 41, 42, ..., 43 are extracted. The extracted lights 41, 42, and 43 having wavelengths of λ ₁ , λ ₂ ,..., Λ _n are input to the light receiving units 86 , 87, and 88 . The light is converted into an electric signal by a photoelectric converter (not shown) in the present embodiment, the signal level is adjusted, and the light is converted into the signal light again, thereby the optical fibers 48, 4
Output to 9 and 50. Note that the extracted λ ₁ , λ ₂ ,.
..., lambda _n of the light 41 of the wavelength, ..., the light receiving unit 85 when outputting as a 43 optical bandpass filter 37
(E.g., a normal light receiving element) that detects whether signal light of a predetermined wavelength is actually input.

Normally, communication is performed in this manner. However, an abnormality occurs in the optical receiving unit 81, for example, the optical band-pass filter 37 or the optical receiving unit 85, and signal light of a specific wavelength cannot be extracted. An abnormality such as loss of frame synchronization may occur in the received signal. In such a case, the optical receiver 84 extracts an optical signal that could not be obtained due to an abnormality due to optical heterodyne reception.
First, when any of the optical receivers 85 detects the occurrence of an abnormality, a control signal to that effect is output to the local oscillation light source 89. Upon receiving this signal, the local oscillation light source 89 outputs light having the same wavelength as that of the abnormal signal light, for example, λ _i .
Then, the oscillating light 93 and the light 83 extraly distributed by the optical distributor 82 are multiplexed, and the multiplexed light is received by the optical receiver 84. On the other hand, the wavelengths λ ₁ , λ
₂ ,..., Λ _n exist.

The multiplexed light received by the optical receiver 84 initially has a random oscillation of the local oscillation light 93, so that the wavefront of the multiplexed light does not coincide with that of the signal light 83, and a predetermined signal light cannot be obtained.
By detecting the light passing through the optical band-pass filter 94, a synchronization signal 95 for matching the wavefront of the distribution wave 83 and the local oscillation wave 93 is output from the optical receiving unit 84 to the local oscillation light source 89. Thus, the wavefronts of the signal light 83 and the local oscillation light 93 match. At this time, the signal light of another wavelength is canceled by the beat component due to the frequency difference from the local oscillation light 93, and the optical band-pass filter 94 does not allow the light of the beat frequency to pass. As the wave light, a signal light having a wavelength λ _i is obtained. By switching and outputting the output from the optical receiving unit 85 from which the signal light could not be extracted due to the abnormality and the optical switching device 69, the light of the wavelength λi which could not be extracted due to the abnormality can be obtained.

Therefore, the redundancy of communication can be increased even when the conventional dual system configuration is not employed. In particular, when extremely high reliability is not required, components such as the optical switches 11 and 12 and other spare transmitters become unnecessary, so that an inexpensive communication device having almost the same reliability as the conventional one can be obtained. it can.

In the above-described embodiment, the frequency multiplexed optical signal is handled. However, when a failure occurs on a receiving side in a part of each frequency-divided signal light, the multiplexing is similarly performed. By providing alternative means for extracting the corresponding signal light from the obtained optical signal, the reliability of the optical communication device can be improved.

[0033]

As described above , according to the first aspect of the present invention, even if some trouble occurs in the processing of a part of the signal light on the receiving side, the signal light can be reproduced by the alternative means. Therefore, reliability can be maintained with a simple configuration without duplicating the communication system. Further, according to claim 1
According to the present invention, the local wave output from the distributed wave and the local oscillation light source is provided.
Supply a synchronization signal to the local oscillation light source to match the wavefront of the vibration wave
So that the signal light of the abnormal system
It can be extracted with high reliability.

[0034]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of an optical communication device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional duplex optical communication device.

FIG. 3 is an explanatory diagram showing an example of each signal light input to the optical communication device.

[Explanation of symbols]

 14, 69 Optical switching device 28 Optical switching device 29, 48 to 50 Optical fiber 37 to 40 Optical band pass filter 81 Optical receiving unit 82 Optical distributor 84 to 88 Optical receiving unit 89 Local oscillation light source

Claims (1)

(57) [Claims] 1. A their respective frequencies of light consisting of specific wavelength
The signal light that has been divided and multiplexed into n systems is
An optical splitter that splits a large number of signal lights, and n systems of the signal lights split by the optical splitter
The signal light of the wavelength of the applicable system is
An optical bandpass filter for extracting Re respectively, extracted from each of the optical bandpass filter of n systems min
System that individually receives signal light of a specific wavelength for each system
Different optical receivers and one of these system-specific optical receivers differ in receiving signal light.
The same as the wavelength of the abnormal signal light when normal occurs
Local oscillation light source that outputs light of different wavelengths as local oscillation light
From the optical distributor to the optical bandpass filter for the n systems.
Receives signal light distribution other than that distributed, and
To match the wavefront of the local oscillation wave output from the local oscillation light source.
And outputs a synchronization signal to the local oscillation light source.
Same as the abnormal signal light output from the local oscillation light source.
An optical heterodyne receiving unit that extracts signal light of one wavelength, and signal lights respectively output from the optical receivers for each system.
Input the signal light output from the optical receiver and
The signal light of the system
An optical communication device, comprising: an optical switching device that switches and outputs a signal light input from a device.