JPH03214832A - Optical communication equipment - Google Patents

Abstract

PURPOSE:To attain an optical communication equipment easily used by providing a specific signal detection means or the like finding out a communication available wavelength not in use from an available wavelength region at desired transmission and detecting a communication destination specific signal when a communication request is detected. CONSTITUTION:An optical transmitter #k (1-k) monitors an optical signal sent from other optical transmitter 1 through a star coupler 2 via an optical branch/ synthesis element 101 and a wavelength variable band pass filter 107 in the optical transmitter #k (1-k) by using a 1st photodetector 108. The optical transmitter #k (1-k) upon the receipt of a transmission request sweeps out a transmission wavelength region of the filter 107 in a communication wavelength region to find out a wavelength lambda2k not in use by other optical transmitter 1 and keeps sending a transmission destination code and its own station code by a light of the wavelength. Then optical transmitter #k (1-k) uses the optical signal of a set wavelength lambda1 to send a communication request signal to an optical receiver #J (6-J) desiring the transmission thereby informing the desired communication. Then the reply from the destination device by the optical signal of the wavelength lambda1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to optical communication devices that perform optical communication with each other via an optical communication medium. [Prior Art] Conventional wavelength division multiplexing optical communication systems enable large-capacity communication by multiplexing dozens to hundreds of light waves by changing their wavelengths little by little and sending them. When increasing communication capacity, it is important to stabilize the oscillation wavelength. For this reason, several methods have been proposed to stabilize the oscillation wavelength. For example, a method has been proposed in which an oscillation frequency is individually assigned to each light source for transmission, and each terminal station manages the oscillation frequency. Another method is to install a central station that manages frequencies, and the central station sends a predetermined reference light to all subscribers, and each subscriber selects a wavelength based on that reference light. A tuning method has been proposed. An example of a method in which the central station manages frequencies is the method described in Japanese Patent Laid-Open No. 63-52528. FIG. 10 shows a block diagram of the principle of this conventional method for central station frequency management, and FIG. 11 shows an example of the system configuration. In FIG. 10, 7010 is a frequency reference light extraction unit that separates the frequency reference light from the light sent from the central station;
0l1 is a heterodyne detection unit that performs heterodyne detection on the frequency reference light, 70l2 is a light source for local oscillation or transmission, 7013 is a tuner that sets the frequency of the light source 7012, and 7014 is a beat signal obtained by the heterodyne detection unit 70l1. 70l5 represents a frequency position detection unit that detects the frequency position by comparing the peak values of adjacent beats. As the frequency reference light, for example, an optical signal obtained by high-speed modulation of the oscillation light of a stabilized light source is sent from the central station to each terminal station, so each terminal station converts the frequency reference light from the light sent from the central station. Frequency reference light is extracted by the extraction unit 7010. The tuner 7013 moves the oscillation frequency of the light source 7012, and the heterolog detection section 70l1 mixes the output of the frequency reference light extraction section 7010 and the output of the light source 7012 to perform heterolog detection. The peak detection section 7014 detects the peak value of the beat signal obtained by detection by the heterodyne detection section 7011. By the tuner 7013, the light source 701
By changing the frequency of 2, a plurality of peak values can be obtained, but the wave number position detection unit 7015 compares the peak values of each adjacent beat to determine which frequency the currently tuned frequency is. It is possible to detect whether it is an FM sideband. In FIG. 11, 7020 is Star Cabra, 7021
is the central office, 7022-1.7022-4 is the terminal station of the subscriber system, and R. is a transmitter, and Tx is a receiver. Each terminal station 7022-1 to 7022-4 is a star coupler 7
Connected by optical fiber via 020. Also,
Central office 7021 is also connected via star coupler 7020. Frequency multiplexing transmission using coherent light is performed, but each terminal station 7022 serves as a reference for frequency setting.
-1 to 7022-4 are not individually managed, but the central office 7021 centrally manages each terminal station 7022-1 to 7022-4.
The frequency reference is sent to 022-4. FIG. 12 shows an example of the arrangement of the frequency standards. When the central station 7021 modulates the oscillation light from the stabilized light source at high speed, for example, from 10 GHz to 50 GH2, as shown in FIG. 12, around the center frequency f0,
{f. ±nf. } sideband appears. Therefore, if the terminal station can detect these sidebands and determine the position of the sideband with respect to the center frequency, the frequency of the light source used for transmission or reception can be set using that position as a reference. For example, the frequency f. and frequency fo+f. During which time, each terminal station's frequency band K. , K. ...K. can be set in many ways. Therefore, when determining the reception or transmission frequency band, the frequency fo +f in the frequency reference light transmitted by each terminal station. By detecting these, a frequency shifted by a predetermined frequency from these reference frequencies may be set. [Problems to be Solved by the Invention] However, in the conventional example described above, the frequency band used by each optical transmitter must be strictly managed and set in order to avoid interference, resulting in the following drawbacks. Ta. (1) When each optical transmitter has an individual reference wavelength light source, the temperature of the light emitting element of each optical transmitter must be precisely controlled to maintain the same reference wavelength. (2) Furthermore, if wavelengths to be used are assigned in advance to each optical transmitter, each optical transmitter cannot use the assigned wavelengths of other optical transmitters, resulting in a decrease in wavelength usage efficiency. [Means for Solving the Problems] The present invention has been made for the purpose of solving the above-mentioned problems, and includes the following configuration as one means for solving the above-mentioned problems. That is, a first wavelength discovery means discovers an unused communicable wavelength from the usable wavelength range when a transmission is desired, and the communication destination specifying signal is continued to be transmitted using the wavelength discovered by the first wavelength discovery means. a first transmitting means, a second transmitting means for outputting a communication request to a communication destination using a control signal communication wavelength in an usable wavelength range, and a second transmitting means for outputting a communication request to a communication destination using a control signal communication wavelength in an usable wavelength range; a receivable signal detecting means for detecting a receivable signal, and a first communication means for communicating with a communication partner using the wavelength discovered by the first wavelength discovering means when the receivable signal detecting means detects a receivable notification signal; communication request detection means for detecting a communication request addressed to the own device in a wavelength for control signal communication; and when the communication request detected by the communication request detection means is detected, a communication destination specifying signal addressed to the own device in a usable wavelength range is provided. a third device that transmits a receivable notification signal at a control signal communication wavelength when the specific signal detection device detects a specific signal;
transmission means. [Function] The above configuration has the function of detecting a wavelength range unused for communication from the wavelength range used for communication, and the function of fixing the wavelength of the transmission light source to the wavelength range (detected wavelength range). An optical transmitter or optical transceiver and an optical receiver or optical transceiver that has the function of detecting the wavelength of light used for communication to the local station from the wavelength range used for communication. By communicating using an unused wavelength range, it is possible to easily manage and set reference wavelengths between each optical transmitter, optical receiver, and optical transceiver, making it extremely easy to use. Optical communication equipment can be provided. [Example] Hereinafter, an example according to the present invention will be described in detail with reference to the drawings. (First Embodiment) FIG. 1 is a configuration diagram of an optical communication system according to an embodiment of the present invention, in which l-1 to 1-n are optical transmitters #l to #n,
2 is a star coupler, 3 is an optical fiber, 4 is an optical branching element, S is an optical fiber, 6-1 to 6-n are optical receivers #1 to #
It is n. FIG. 2 is a block diagram showing the detailed configuration of the optical transmitter 1 shown in FIG. 1. In FIG. 2, 101 is a light branching and merging element, 102 is a light merging element, 103 is a first optical isolator, and 104 is a second optical isolator.
An optical isolator, 105 is a first light source that is, for example, a semiconductor laser that oscillates at a certain wavelength, 106 is a variable wavelength light source that is, for example, a semiconductor laser that can change the oscillation wavelength, and 107 is a wavelength of transmitted light. 108 is a first photodetector; 109 is a bandpass filter that transmits only light of a certain wavelength; 110 is a second photodetector; 111 is a light branching element; 112 is an optical transmission including the operation of a first light source 105, a variable wavelength light source 106, a variable wavelength bandpass filter 107, a first photodetector 108, and a second photodetector 110 in order to transmit data from the terminal Isoki. This is a control circuit that controls the entire machine. In the above-mentioned configuration, the light branching and merging element 101, the light merging element 10
2. The optical branching element 111 is composed of, for example, a half mirror or a beam splitter. The wavelength tunable light source 106 is, for example, a wavelength tunable DBR semiconductor laser having a DBR mirror having a structure that can change the Bragg wavelength by injecting carriers into a DBR (distributed reflection mirror) region. By adjusting the amount of carrier injection, the oscillation wavelength can be continuously changed. This wavelength variable light source 1
06, for example, K. κOTAKI, M. M
ATYUDA, M. YANO. H. ISHIKAWA
,H. IMAI! = Yotte 1987 El
electronics Letters magazine Vol. 23 No. 7 No. 3
The structures described on pages 25-327 can be used. Here, it is assumed that the variable wavelength light source 106 includes a wavelength adjustment section that changes the oscillation wavelength of the wavelength tunable light source 106, and an output light modulation section that modulates the intensity of output light. Tunable wavelength DBR
In the case of a semiconductor laser, the DBR section corresponds to a wavelength adjustment section, and the active region corresponds to an output light modulation section. Furthermore, the wavelength tunable band lower pass filter 107 includes a wavelength tunable DBR (distributed reflection type Bragg mirror) (for example, the one described in Japanese Patent Laid-Open No. 175025/1982) that changes its Bragg wavelength by carrier injection as described above. This can be achieved by using FIG. 3 is a block diagram showing details of the optical receiver 6. In FIG. 3, 6Ql is a demultiplexer, 602 is a first photodetector, and 603 is capable of changing the wavelength range of transmitted light. 604 is a second photodetector, 605 is a control circuit that controls the entire optical receiver, 606 is a wavelength tunable bandpass filter;
is a first light source that is, for example, a semiconductor laser that oscillates at a certain wavelength. The variable wavelength bandpass filter 603 in FIG.
A filter having the same configuration as the variable wavelength bandpass filter 107 in the optical transmitter 1 shown in FIG. 2 can be used. Regarding the communication operation of this embodiment with the above configuration, the fifth
This will be explained below with reference to the figure and the flowchart of FIG. 5 shows communication control of the optical transmitter 1, and FIG. 6 shows communication control of the optical receiver 6. As shown in FIG. 4, the wavelength band used is divided into one wavelength (λ1) that can be easily separated and another wavelength group (λ2 group). One wavelength is the wavelength used to set up each other's lines prior to communication, and is referred to here as the setting wavelength.
The wavelengths in the other wavelength group (λ2 group) are wavelengths used for data communication during actual transmission and reception, and are referred to as a communication wavelength range. The following explanation is from the K-th optical transmitter #K (1-K) to the J
The procedure for communicating to the th optical receiver (6-J) will be explained as an example. For example, the K-th optical transmitter #K (1-K) transmits the optical signal transmitted by the other optical transmitter 1 through the star coupler 2 to the optical signal in the optical transmitter #K (1-K). Branch/merging element 1
01 and the first through the wavelength variable bandpass filter 107.
It can be monitored by photodetector 108. When receiving a transmission request, the optical transmitter #K (1-K) proceeds from step S1 to step S2 in FIG. 5, and first sweeps the transmission wavelength range of the variable wavelength bandpass filter 107 within the communication wavelength range. Then, in the communication wavelength range, a wavelength (λ28) that is not used by another optical transmitter 1 is found, and in step S3, the transmitting partner code and own station code, which are communication partner identification signals, are immediately transmitted using light of that wavelength. Continue sending. On the other hand, the optical transmitter #K (1-K) uses the setting wavelength (
Optical receiver #J that wishes to transmit using an optical signal of λ1)
Send a communication request signal to (6-J) and tell it that you want to start communication. Then, in step S4, the setting wavelength (λ1
) waits for a response from the other device using an optical signal. Here, in the communication system of the control signal system using the setting wavelength (E,), each optical transmitter 1 and each optical receiver 6 must be able to communicate with any optical transmitter 1 or optical receiver 6 once within a certain period of time. The condition is that transmission can be performed to the optical receiver 6. For this reason, in this embodiment, for example, a time division communication method is used. On the other hand, the optical receiver #J (6-J) always uses the first photodetector 602, as shown in step S51 in FIG.
It monitors the signal of the setting wavelength (e,) flowing on the optical communication line, and can know whether or not a communication request addressed to its own station is flowing on the line. When the optical receiver #, J (6-J) detects that communication addressed to its own station is requested as a result of monitoring the setting wavelength (λ1), the process proceeds from step S51 to step S52, and the optical receiver #, J (6-J) proceeds to step S52 from step S51, Check whether reception is being performed. If the own device is receiving, step S5
Proceed to step 3, and use the setting wavelength (λ,) to send a signal to the destination device, optical transmitter #K (1-K), indicating that communication is not possible.
Send to. On the other hand, if it is not currently receiving and can be received, step S5
Proceeding to step 5, the signal output of the second photodetector 604 is checked, the transmission wavelength range of the variable wavelength bandpass filter 603 is swept within the communication wavelength range (λ2), and the optical signal transmitting the own station code is detected. Performs processing to detect wavelength. When the wavelength is detected, the process proceeds to step S56, where the optical receiver #J (
6-J) uses light of the setting wavelength (λ1) to detect the communication wavelength from the other party, and sends a receivable notification signal to the other party of the communication request, indicating that communication is possible. Transmit to transmitter #K (1-K). The optical transmitter #K (1-K) that has output the communication request is in a state of waiting for a response in step S4, and this receiver #J (
It is possible to receive the response signal outputted in step S53 or step S55 using the light of the setting wavelength (λ1) from 6-J). As a result, optical transmitter #K
The process of (1-K) proceeds from step S4 to step S5, where it is checked whether the received response signal is a receivable notification signal or not. In S6, it is notified that the transmission request cannot be sent, and the process returns to step Sl to prepare for the next transmission request. On the other hand, if the received signal is a receivable notification signal, the process advances from step S5 to step SIO and starts communication addressed to optical receiver #J (6-J) using the communication wavelength (Eyo). do. Similarly, the optical receiver #J (6-J) also performs step S5 in FIG.
7, data is received from the optical transmitter #K (1-K). As explained above, according to this embodiment, it is possible to easily manage and set reference wavelengths between each optical transmitter and optical receiver, and an optical communication device that is extremely easy to use is provided. can. (Second Embodiment) FIG. 7 is a system configuration diagram of an optical communication system according to a second embodiment of the present invention.
1001-n are optical transmitters #1 to #n, 1002 is a first optical star coupler, 1003 is an optical fiber, and 1004 is a second optical star coupler. Optical transceivers #1 to #n and 1001-1 to 1001-
The configuration of n is a device that has both the functions of the optical transmitter and optical receiver of the first embodiment shown in FIG. The only difference is that Next, the operation of the second embodiment having the above configuration will be explained. First, the wavelength used in this example will be explained. The wavelength of light used for communication is divided into two wavelengths, similar to the first embodiment shown in FIG. One wavelength is used for setting up a communication line, and the other wavelength is used for actual communication, and these wavelengths can be easily separated from each other. Therefore, as shown in FIG. 4, the wavelength for actual communication is composed of light of several wavelengths that are close to each other. The following description is based on optical transceiver #1 (1001-1),
The case where communication is performed with optical transceiver #n (1001-n) will be described as an example. Optical transceiver #1 (1
001-1) sends a sweep signal from the control circuit 112 to the wavelength tunable bandpass filter 107, and transmits a sweep signal to the communication wavelength range (λ
2) The transmission wavelength range of the wavelength tunable bandpass filter 107 is swept. Further, the output signal from the first photodetector 108 is output to the control circuit 112. The control circuit 112 recognizes the presence or absence of arriving light from the input signal, and fixes the transmission wavelength range of the wavelength tunable bandpass filter 107 at an empty wavelength with no arriving light (this wavelength is the communication wavelength (λ2 1-n )). The control circuit 112 determines the center wavelength of the transmission wavelength range of the wavelength tunable band pass filter 107 from the sweep signal output to the wavelength tunable band pass filter 107. A control signal is output to the wavelength adjustment section so that the oscillation wavelength becomes the same as the transmission center wavelength of the wavelength tunable bandpass filter 107. Furthermore, the local station code and each destination are alternately sent to the output light modulation section of the wavelength tunable light source 106. The control circuit 112 starts transmitting an optical signal in which the local station code and the destination code are alternately repeated.Following this operation, the control circuit 112 changes the communication method of the setting wavelength (λ1) by the first light source 105 described above. Therefore, the optical transceiver #n of the other party with which you are trying to communicate now
(1001-n) transmits communication request data indicating that it wants to start communication. On the other hand, each optical transceiver 1001 always receives the light of the setting wavelength (λ,) transmitted by the bandpass filter 109 at the second photodetector 110, and outputs the communication contents to the control circuit 112. That is, the control circuit 112 constantly monitors the communication content within the setting wavelength (λ,). Therefore, by monitoring the setting wavelength (λ1), the optical transceiver #n (1001-n) can know whether another optical transceiver 1001 is requesting communication to its own station. Optical transceiver #n (1001-n) is connected to other optical receiver 1
When the communication request signal from 001 is recognized, the setting wavelength (
The other party's code is known from the communication content of λ1). and,
Next, in order to sweep the transmission wavelength range of the wavelength tunable bandpass filter 107 within the communication wavelength range (λ2), the control circuit 1
12 outputs a control signal to the variable wavelength bandpass filter 107 to start the sweep operation. At the same time, the content of the optical signal received by the first photodetector 108 is transmitted to the control circuit 1.
Begin to decipher by 12. As a result of signal decoding of the control circuit 112, the setting wavelength (λ1)
The transmission wavelength of the variable wavelength bandpass filter 107 is fixed so as to transmit the detected wavelength. The control circuit 112 learns the center wavelength transmitted by the wavelength tunable band pass filter 107 from the control signal output to the wavelength tunable band pass filter 107, and adjusts the wavelength of the wavelength tunable light source 106 so as to output light at the same wavelength. Outputs a control signal to the section. Control circuit 112 of transmitter/receiver #n (1 00 1-n)
Following these operations, transmits a communication enable signal indicating that preparations for communication are completed to the first light source 105 according to the communication method of the setting wavelength (λ,), and optical transceiver #1
(1001-1). Optical receiver #1 (1001-1) has a wavelength for setting (λ1
), and optical transceiver #n (1001-n)
Detects a communicable signal from the other party (optical transceiver #n)
Knowing that lOO1-n) is ready, it begins communication using the communication wavelength (Eyo, -7). In the case of this communication method, two-way communication is performed by alternately using communication wavelengths (λ21-,) in both optical transceivers. In addition, if the optical transceiver #n (1001-n) is already communicating with another optical transceiver "fool", or if it is impossible to communicate in the state of the terminal device, the setting wavelength (round ) using optical transceiver #1 (1001-1
) to indicate that communication is not possible. In this case, should we give up communication to the optical transceiver #n (1001-n), or should we enable communication? I'll have to wait for it to arrive. (Third Embodiment) In the embodiment described above, two-way communication is performed using one communication wavelength, but each optical transceiver 1001-1 and 1001-n uses a different communication wavelength. (λ2■,
It is also possible to perform bidirectional communication by setting λ2 n-1 ). The third method according to the present invention when such two wavelengths are used
The line setting procedure in this embodiment will be explained below. The following description will be made using communication between optical transceiver #1 (1001-1) and optical transceiver #n (1001-n) as an example. Optical transmitting/receiving device #1 that received a communication request from a terminal device
(1001-1) sends a sweep signal from the control circuit 112 to the wavelength tunable band pass filter 107 to sweep the transmission wavelength range of the wavelength tunable band pass filter 107 in the communication wavelength range (λ2). Further, the output signal from the first photodetector 108 is transmitted to the control circuit 1
12, the control circuit 112 recognizes the presence or absence of light from the input signal, and fixes the transmission wavelength range of the wavelength tunable bandpass filter 107 at a wavelength where there is no light (an unused wavelength). Communication wavelength (λ2 in
). The control circuit 112 includes a variable wavelength bandpass filter 107.
The center wavelength of the transmission wavelength range of the variable wavelength bandpass filter 107 is determined from the sweep signal output to the wavelength tunable bandpass filter 107. moreover,
The control circuit 112 outputs a control signal so that the wavelength output by the wavelength tunable light source 106 becomes the same as the transmission center wavelength of the wavelength tunable bandpass filter 107. Then, the local station code and the destination code are alternately outputted to the output light modulation section of the wavelength tunable light source 106, and an optical signal in which the local station code and the destination code are alternately repeated begins to be transmitted. Following this operation, the control circuit 112 sends the signal from the first light source 105 to the other party's optical transceiver #n ('l O O
1-n) transmits communication request data indicating that it wants to start communication. Optical transceiver #n (1001-n) that received the communication request,
If optical communication is not possible, such as when the terminal device is already communicating with another optical transceiver 1001 or when the terminal device is not in a communicable state, a communication disable signal indicating this is sent to the setting wavelength (λ1). According to the communication method, the optical transmitter/receiver #1 (1001-1) that received the communication request is sent back. On the other hand, it is not in communication with another optical transceiver 1001.
If the terminal device is in a state where communication is possible, the control circuit 112 outputs a wavelength sweep signal to the wavelength tunable band pass filter 107, and sweeps the transmission wavelength of the wavelength tunable band pass filter 107 in the communication wavelength range (λ2). to find wavelengths where there is no light (unused wavelengths). Then, the control circuit 112 controls the wavelength tunable bandpass filter 1 from the sweep signal.
Detect the transmission center wavelength of 07. and wavelength tunable light source 1
A control signal is output to the wavelength adjustment section of 06, and the wavelength variable light tA
106 and the transmission center wavelength of the variable wavelength bandpass filter 107 are made to match (this wavelength is hereinafter referred to as the communication wavelength (λZ n-+ )). Subsequently, the control circuit 112 outputs the local station code and the other party's code to the output light modulation section of the wavelength tunable light source 106. As a result, the transmission of the local code and the other party's code at the wavelength (λ2 n-1 ) is repeated. Next, the optical transceiver #n (1 00 1-n) uses the communication wavelength (92
1-'r+). The wavelength variable bandpass filter 107 is controlled by the control circuit 112.
outputs a sweep signal to the communication wavelength range (λ2), detects the wavelength of the optical signal sent from optical transceiver #1 (1001-1> to its own station), and detects the wavelength ( λz
l-n) to fix the transmission center wavelength of the variable wavelength bandpass filter 107. The communication preparation is now complete, so after the above operations are completed, the optical transceiver #n (1 00 1-n) uses the setting wavelength (λl) to transmit the optical transceiver #1' (lO 0
1-1) sends a signal to notify that communication is ready. ? Transmitter/receiver #1 (1001-1) has a setting wavelength (
λ1) signal, the optical transceiver #n (100
1-n) is ready, the other party's optical transceiver #n (
1001-n), and transmits data. On the other hand, after obtaining the communication start signal, the optical transceiver #n (1001-n) also uses the communication wavelength (λ2) if necessary.
n-1) to transmit data. (Fourth Embodiment) A fourth embodiment according to the present invention is shown in FIG.
This will be explained below with reference to FIG. FIG. 8 is a block diagram showing the configuration of the optical transmitter 1 according to the fourth embodiment of the present invention, and FIG. 9 is a block diagram showing the configuration of the optical receiving shore 6 of the fourth embodiment. Note that the communication system configuration diagram in this embodiment has the configuration shown in FIG. In FIG. 8, 1101 is a light branching/merging element, 1l02
110 is a light combining element, 1103 is a first optical isolator, and 110 is a first optical isolator.
4 is a second optical isolator, 1105 is a first light source, 110
6 is a wavelength tunable light source, 1107 is an optical switch that allows you to select one of two optical paths, and the optical switch 110
7 can change the direction in which the light travels by a control signal from the control circuit 1113. 1108 is a light branching element, 1109
is a light combining element, 1110 is a bandpass filter, 111
1 is a second photodetector, 1112 is a first photodetector, 1113
is a control circuit that controls the entire optical transmitter 1. In FIG. 9, 1601 is a demultiplexer, 1602 is a first photodetector, 1603 is a light combining element, 1604 is a variable wavelength light source, 1605 is a second photodetector, and 1606 is a control circuit. The communication control method in the fourth embodiment having the above configuration is basically the same as that in the first embodiment described above. 1st
The difference from the embodiment lies in the control for searching for a communication wavelength. The wavelengths used for communication are composed of a setting wavelength (Eyo) and a communication wavelength range group (λ2 group), as in the first embodiment shown in FIG. The following explanation is from optical transmitter #l (1-1) to optical receiver #
5 (6-5) as an example. The control circuit 1l13 of the optical transmitter #1 (1-1) receives a signal from the terminal Isoki to the terminal equipment connected to the optical receiver #3 (6-3) to the effect that data has been transmitted. Then, a wavelength that is not used by other optical transmitters 1 is searched for in the communication wavelength range (λ2). This operation is performed as follows. That is, the control circuit 11
13 outputs a control signal to the optical switch 1107, and the light output from the wavelength tunable light source 1106 passes through the light combining element 11.
09, and can be input to the first photodetector 11l2. In this state, the first photodetector 11l2
Light from variable wavelength light source 1l06 and star cutlet 2
Light from the line (hereinafter referred to as light on the line) is superimposed and input. Then, by square-law detection by the first photodetector 1112, an electric signal obtained by heterodyne detection of the two lights is output to the control circuit 1113. In this state, if there is no light on the line, the signal output from the first photodetector 1l13 is only direct current.
On the other hand, when there is an optical signal on the line, an electrical signal (beat signal) having a frequency that is the difference between the frequency on the line and the frequency of the light from the wavelength tunable light source 1106 is output. For example, the wavelength of the light from the wavelength tunable light source 1106 is 880 nm.
If the light on the line is 881 nm, then about 3 8 6
A GHz beat signal is output. However, when trying to transmit signals using an actual electrical system,
Several tens of GH. is the limit, and the control circuit 1113 cannot receive a high frequency beat signal close to 400 GH2 as in the above example. In this case, an electrical filter (several tens of GHz
width). As a result, if it is possible to electrically receive up to 2 GHz signals and the wavelength of the wavelength tunable light source 1106 is 880 nm, the wavelength is 880 nm.
This has the same effect as providing an optical filter having a half width of 0.011 nm around m. The wavelength of the wavelength tunable light source 1106 is set to the communication wavelength range (λ2).
By performing a medium sweep and monitoring the beat signal from the first photodetector 1112, a usable communication wavelength (λ2 1-13 ) can be found without interfering with other communication signals. Moreover, the wavelength of the wavelength tunable light source 1106 can be set to the communication wavelength (λ2 1-IS ). Once the communication wavelength (λ2l~,) has been determined as described above, the control circuit 11l3 outputs a control signal to the optical switch 1107, and the light output from the wavelength tunable light source 1106 is directed toward the star coupler 2. light switch 11 to avoid
Change the status of 07. Further, the control circuit 1113 outputs the local code and the other party code to the output light modulation section of the wavelength tunable light source 1106, and transmits them as optical signals to the communication desired device. Following this operation, the control circuit 1113 controls the first light;
According to the communication method of the setting wavelength (λ1) using
6-5) Notify 'r that there is a communication request from optical transmitter #1 (1-1). After that, optical transmitter #1 (1-1) is transferred to optical receiver #5 (
6-5) waits for information indicating that it is ready to be received to be returned using the setting wavelength (λl). Next, the operation of optical receiver #5 (6-5) shown in FIG. 9 will be explained. The first photodetector 1602 in optical receiver #5 (6-5) constantly monitors the communication content of the setting wavelength (λ,), and if any of the optical transmitters 1 Machine #5 (6-
5) It is possible to immediately know whether or not a communication is requested to the addressee. When receiving a communication request from optical receiver 1, if it has already received a signal from another optical transmitter 1, or if the terminal device is not in a state where it can receive, optical receiver #5 (6 −
The control circuit 1606 in 5) outputs a signal to the first light source 1607, and transmits a signal to the optical transmitter l that has requested communication, informing it that communication is not possible, according to the communication method of the setting wavelength (λ,). do. Further, if the optical transmitter #5 (6-5) is in a communicable state when receiving the communication request, the control circuit 1606 sweeps the wavelength range (λ2) for communication using the wavelength of the wavelength tunable light source 1604. A control signal is output to cause the wavelength variable light source 1604 to emit light. The light output from the wavelength tunable light source 1604 passes through the merging element 1
603, it is combined with the light on the line and sent to the second light source detector 1605, where it is square-law detected. The control circuit 16o6 monitors the beat signal at this time, finds the light of the wavelength (λ2 1-6) that is transmitting its own station code and the station code of optical transmitter #1 (1-5), and adjusts the wavelength. The wavelength of the output light from the light source 1604 is fixed. The control circuit 1606 controls the communication between the partner station {optical transmitter #1 (1-5)
} After finding the wavelength (λ! +-5) of the optical transmitter #1 (1-5), the first
Outputs control signals and the like for the light source 1607. On the other hand, at this time, the optical transmitter #1 (1-1) constantly monitors the setting wavelength (n.) using the second photodetector 1l11. Therefore, optical receiver #5 (6-5)
Upon learning that it is now possible to receive optical transmitter #1 (1
-1) then starts desired data communication using the communication wavelength (λ21-1+) that is transmitting the own station code and the other station code. From now on, optical transmitter #1 (1-1) and optical receiver #5 (6-
5) and the termination procedure is performed using this communication wavelength (λ2
1-1! ). In the above four embodiments, a semiconductor laser was basically used as the light source, but the present invention is not limited to the above examples.
Of course, a single gas laser, solid state laser, dye laser, etc. may also be used. Furthermore, in the above embodiments, each optical transmitter, optical receiver, and optical transceiver are constructed using semiconductor elements, but of course they may be constructed using other optical components having similar effects. is obvious. In addition, various modifications can be applied without departing from the scope of the present invention. As explained above, according to this embodiment, by sweeping the transmission wavelength band of an optical bandpass filter or a device having a similar effect within each optical transmitter within the wavelength band used for communication, It is possible to find a wavelength band in which communication cannot be received by the photodetector of the optical transmitter and receive it with light of that wavelength, and the absolute wavelength management within each optical transmitter is more relaxed than before. Moreover, since the optical transmitters that can use the unused wavelength range are not limited, the efficiency of using the wavelength range used for communication can be improved. [Effects of the Invention] As explained above, according to the present invention, reference wavelengths can be managed and set between each optical transmitter, optical receiver, and optical transceiver with a degree of freedom, making it extremely usable. We can provide optical communication equipment that is easy to use.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an optical communication system according to an embodiment of the present invention; FIG. 2 is a block diagram of an optical transmitter according to a first embodiment of the present invention constituting the optical communication system of FIG. 1; FIG. 3 is a block diagram of the optical receiver of the first embodiment of the present invention that constitutes the optical communication system of FIG. 1; FIG. 4 is a diagram showing the allocation of wavelengths used for communication in this embodiment; FIG. 5 is a communication control flowchart for the optical transmitter according to the first embodiment, FIG. 6 is a communication control flowchart for the optical receiver according to the first embodiment, and FIG. 7 is an optical communication system according to the second embodiment of the present invention. FIG. 8 is a block diagram of an optical transmitter according to a fourth embodiment of the present invention; FIG. 9 is a block diagram of an optical receiver according to a fourth embodiment of the present invention; 2 FIG. ~No. 11! FIG. 1 is a diagram for explaining a conventional example. In the figure, 1... optical transmitter, 2,1002.1004...
・Star Katsupura, 3.1003...Optical fiber, 4
, 111.1108... Optical branching element, 5... Optical fiber, 6... Optical receiver, 101, 1101.1608
... Optical branching/merging element, 102, 1102, 1109.
1603... Light combining element, 103, 104, 1103
．． 1104... Optical isolator, 105,605,1
105.1607...first light source, 106,603,1
106.1604... Tunable wavelength light source, 107... Tunable wavelength band pass filter, 108, 110, 602,
1111, 1112, 1602, 1605...Photodetector, 109.1110...Bandpass filter, 11
2,605,1113.1606...control circuit, 60
1, 1601... Demultiplexer, 604... Second photodetector, 1001... Optical transceiver, 1107... Optical switch. Patent Applicant Canon Co., Ltd. 11＾≦ Figure 3 λ2 Figure 4 Figure 5 Figure 6 Figure ○

Claims (3)

[Claims] (1) In optical communication devices that perform optical communication with each other via an optical communication medium, a first wavelength discovery means for discovering an unused communicable wavelength from a usable wavelength range when a transmission is desired; and the first wavelength discovery. a first transmitting means that continues to transmit a communication destination specifying signal using a wavelength discovered by the means; and a second transmitting means that outputs a communication request to a communication destination using a control signal communication wavelength in an usable wavelength range. a receivable signal detection means for detecting a receivable notification signal from a communication partner from a control signal communication wavelength in the usable wavelength range; and when the receivable signal detection means detects a receivable notification signal, the first a first communication means for communicating with a communication partner using the wavelength discovered by the wavelength discovery means; a communication request detection means for detecting a communication request addressed to the own device using the control signal communication wavelength; and the communication request detection means. a specific signal detection means for detecting a communication destination specifying signal addressed to the own device in a usable wavelength range when a communication request is detected by the control signal detection means; An optical communication device comprising: third transmitting means for transmitting a receivable notification signal. (2) The optical communication device according to claim 1, wherein bidirectional optical communication is performed using the only communicable wavelength discovered by the first wavelength discovery means. (3) The optical communication device according to claim 1, wherein bidirectional optical communication is performed using a communicable wavelength discovered by the first wavelength discovery means and a wavelength different from the discovered communicable wavelength. .