JPH0669884A - Optical parallel transmitter - Google Patents

Abstract

PURPOSE:To simplify mounting in an optical transmitter by using an optical receiver for detecting an optical output level and to enable automatic optical output control by using average value detection by using a synchronizing signal for detecting the optical output level. CONSTITUTION:At a down optical channel, the output light of a laser 120 is transmitted and converted to a voltage by a photodetector 140 and an amplifier circuit 130, and a time average value is detected by a detection circuit 160. Corresponding to the detection output, a pulse duration modulation circuit 180 performs E/O conversion while controlling a frame synchronizing signal width and afterwards, the signal is transmitted to the transmission side of the down optical channel. Then, the signal restored to the voltage is detected by a pulse duration detection circuit 165 and restored to the photodetection level information of the photodetector 140. At such a time, a bias current control circuit 170 controls the bias current of the laser 120 so as to fix the output of the detection circuit 165. The automatic output control is similarly performed to an up optical channel as well. Thus, the automatic optical output control is enabled to parallel data containing burst in the simple optical mounting form.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission device between information processing devices or in an information device.

[0002]

2. Description of the Related Art Reduction of transmission line size and increase in capacity of parallel transmission lines between information processing devices or in information devices, EMI resistance
In order to improve the property, optical parallel transmission using an optical fiber as a transmission line has been attracting attention instead of parallel transmission by electricity. In this optical parallel transmission system, a semiconductor laser is used as a light emitting element in order to set the transmission rate per channel to several hundred Mb / s or more.

Since the threshold of oscillation of the semiconductor laser has temperature dependency, an automatic light control for controlling the bias current applied to the semiconductor laser is so set that the output level of the optical transmitter becomes constant even if the temperature of the device changes. Output control (APC) needs to be performed. When an optical parallel transmission apparatus is configured by using a plurality of optical transceivers, if the optical transmitter of each channel individually performs automatic optical output control, the size and cost required for the controller increase. Usually, in order to perform automatic light output control, a light receiving element is arranged close to a semiconductor laser to be controlled in the optical transmitter. In order to reduce the size and cost of the optical parallel transmission apparatus, it is effective to form an array of light emitting elements and light receiving elements, but when an array semiconductor laser is used, it is extremely difficult to arrange the light receiving elements.

Conventionally, in order to reduce the cost of automatic optical output control of an optical parallel transmission apparatus composed of a plurality of optical transceivers,
The techniques described as the first conventional example and the second conventional example have been used below.

A first conventional example will be described with reference to FIG.
FIG. 4 is a block diagram of a bidirectional optical parallel transmission device. As described in JP-A-3-34633, a reception level detection circuit 16 connected to each optical receiver of an optical channel
1 and 261 detect the optical reception level, the reception level information of each channel is multiplexed by the multiplexing signal generator 310, and the transmitters 320 and 420 and the transmission lines 300 and 4 are used.
00, receivers 330 and 430, multiplexed signal decompressor 3
Bias current control circuit 1 for controlling the bias current of each optical transmitter by light or electricity by 40 and 440.
71, and automatic optical output control was performed in each optical transmitter according to the optical reception level information transmitted to the optical transmitter side.

In the second conventional example, as shown in FIG. 5, the light receiving elements 195 and 295 are arranged only in the optical transmitter of one of the optical channels forming the parallel transmission system, and the optical transmission of the channel is performed. The optical output levels of the optical transmitters for all channels are controlled based on the optical transmission output level information.
As a channel for monitoring the optical transmission output level information, a sync signal transmission channel without mark rate fluctuation is usually used.

[0007]

However, in the first conventional example, it is necessary to add a transmission line for transmitting the reception level information, which has a drawback that the cost of the transmission line increases. In addition, there is a drawback in that a compensating circuit must be provided to handle burst signals that frequently occur in the parallel transmission system in the information processing device. As a signal detection method for automatic light output control, there are average value detection and peak value detection. However, in a burst signal transmission system, mark rate fluctuation is significant, so peak value detection must be performed.
In order to perform automatic optical output control on a burst signal by peak value detection, it is necessary to detect the peak value at the rising edge of an arbitrary bit and then perform control within the duration of the bit. However, in the first conventional example, it takes at least a time for the pulse to make a round trip between the transmitter and the receiver until the optical output pulse is transmitted by the optical transmitter and the reception level information is returned to the optical transmitter. Unless compensation is performed, automatic optical output control cannot be performed on burst signals.

In the second conventional example, since a synchronization signal transmission channel without mark rate fluctuation can be used as a channel for monitoring the optical transmission output level information, the problem of burst signal correspondence can be avoided. . However, even if there is only one channel, the light receiving element must be arranged in the optical transmitter, and there is a drawback that optical mounting becomes difficult especially when the light emitting element is arrayed.

An object of the present invention is to provide an optical parallel transmission apparatus capable of performing automatic optical output control for burst signals with a low cost and a simple optical mounting form.

[0010]

In order to solve the above-mentioned problems, in an optical parallel transmission apparatus for performing signal transmission by a plurality of optical channels including a synchronous signal transmission channel, an optical receiving section for detecting the reception level of the synchronous signal transmission channel. When,
Depending on the optical reception level information transmitting means for transmitting the optical reception level information of the synchronization signal transmission channel to the optical transmission side of the plurality of optical channels, and the optical reception level information of the synchronization signal transmission channel transmitted to the optical transmission side. And a transmission level control unit that controls the transmission levels of the plurality of optical channels to configure an optical parallel transmission apparatus.

In order to achieve the above object, in a bidirectional optical parallel transmission apparatus that performs signal transmission by a plurality of optical channels including a synchronization signal transmission channel, intensity information of an optical signal propagating through a transmission line is converted into a reverse synchronization signal. An optical parallel transmission apparatus having a synchronous signal transmission channel transmitter / receiver for superimposing and transmitting on the optical signal and a transmission level control unit for controlling transmission levels of the plurality of optical channels according to intensity information of the optical signal. To do.

[0012]

According to the present invention, since the optical receiver is used for detecting the optical output level of the optical transmitter instead of the light receiving element in the optical transmitter, the optical mounting can be simplified. Furthermore, since the synchronizing signal continuously transmitted without fluctuation of the mark ratio is used for detecting the optical output level, automatic optical output control can be performed using either average value detection or peak value detection. Since the optical output level information received by the optical receiver is transmitted by being superimposed on the synchronization signal for reverse transmission, it is not necessary to add a transmission path for transmitting the reception level information.

[0013]

EXAMPLES The present invention will be described in more detail below with reference to examples. FIG. 1 is a block diagram showing a first embodiment of the present invention, showing the configuration of a bidirectional optical parallel transmission apparatus.
Driving circuits 110 and 210, semiconductor lasers 120 and 220, optical fibers 100 and 200, light receiving element 1
An optical channel composed of 40 and 240, amplification circuits 130 and 230, and identification circuits 150 and 250 is
These are downlink and uplink clock signal transmission channels, respectively. Similarly, drive circuits 111 and 211, semiconductor lasers 121 and 221, optical fibers 101 and 201, light receiving elements 141 and 241, and an amplifier circuit 131.
And 231 and the identification channels 151 and 251 are optical channels for downlink and upstream frame signal transmission, respectively. Also, the drive circuit 112-
11N and 212-21N, semiconductor lasers 122-1
2N and 222-22N, optical fiber 102-10N
And 202 to 20N, light receiving elements 142 to 14N and 242 to 24N, and amplifier circuits 132 to 13N and 232.
23N, identification circuits 152-15N and 252-25
The optical channels constituted by N are downlink and upstream data signal transmission channels, respectively. The threshold currents for oscillation of the semiconductor lasers 120 to 12N and 220 to 22N are equal to each other.

The automatic optical output control operation of the downstream optical channel will be described as an example. The output light of the semiconductor laser 120 of the clock signal channel is transmitted to the receiver by the optical fiber 100 and converted into a voltage proportional to the received light level by the light receiving element 140 and the amplifier circuit 130. The time average value of the same voltage is detected by the average value detection circuit 160.
The pulse width modulation circuit 180 controls the pulse width of the frame synchronization signal according to the output of the average value detection circuit 160. That is, as shown in the waveform explanatory view of FIG.
When the light receiving level of is low, a narrow pulse is output, and when it is high, a wide pulse is output. At this time, the rising start time of the frame synchronization signal pulse is constant regardless of the pulse width. The frame synchronization signal pulse voltage of the upstream optical channel whose pulse width is controlled by the pulse width modulation circuit 180 is applied to the drive circuit 211 and the semiconductor laser 221.
After being E / O converted by the optical fiber 201, it is transmitted to the transmitter side of the downstream optical channel by the optical fiber 201 and is restored to a voltage signal by the light receiving element 241 and the amplifier circuit 231. The pulse width of the synchronization signal pulse of the upstream optical channel restored to the voltage is detected by the pulse width detection circuit 165 and restored to the light reception level information of the light receiving element 140. In the bias current control circuit 170, the pulse width detection circuit 16
The bias current of the semiconductor laser 120 is controlled through the drive circuit 110 so that the output of 5 becomes constant. The bias current control circuit 170 also includes the drive circuits 111 to 11
The bias current of the semiconductor lasers 121 to 12N is controlled to be equal to the bias current of the semiconductor laser 120 through N.

Similarly, automatic optical output control is performed on the upstream optical channel.

By using the control signal transmission path described above, automatic optical output control can be performed without incorporating a light receiving element in the optical transmitter and without adding a transmission path for transmitting the control signal. It can be carried out. Moreover,
Even if a burst signal is transmitted on the data signal channel, it does not affect the automatic optical output control operation.

Next, a second embodiment will be described with reference to FIG. In the second embodiment, the upstream clock signal channel is used for transmitting the light reception level information received by the light receiving element 140 of the downstream clock signal channel. Second
In the embodiment, since the pulse width of the clock signal is modulated according to the optical output level of the optical channel in the opposite direction, it is not possible to correctly evaluate the light reception level with the average value of the clock signal. Circuit is used. A voltage proportional to the received light level is generated by the light receiving element 140 and the amplification circuit 130, and the peak value of the voltage is detected by the peak value detection circuit 190. The pulse width modulation circuit 180 controls the pulse width of the frame synchronization signal according to the output of the peak value detection circuit 190. The clock signal pulse voltage of the upstream optical channel whose pulse width is controlled by the pulse width modulation circuit 180 is E / O converted by the drive circuit 210 and the semiconductor laser 220, and then transmitted by the optical fiber 200 to the transmitter of the downstream optical channel. And is restored to a voltage signal by the light receiving element 240 and the amplifier circuit 230. The pulse width of the same voltage is detected by the pulse width detection circuit 165. The operations of the pulse width detection circuit 165 and the bias current control circuit 170 are similar to those of the first embodiment.

In the first and second embodiments described above, the space division optical parallel transmission system in which one optical fiber is assigned to each upstream and downstream optical channel has been used. One optical wavelength is assigned, the signal light transmitted from each channel is combined by a multiplexer, the combined light is transmitted by one optical fiber, and the combined light is demultiplexed for each wavelength by a demultiplexer. After that, the wavelength division optical parallel transmission method of receiving by the optical receiver of each channel may be used.
Further, a method in which space division optical parallel transmission and wavelength division optical parallel transmission are combined may be used.

In the first and second embodiments, the pulse width modulation of the synchronizing signal is used as a means for superposing the intensity information of the optical signal propagating through the transmission line on the synchronizing signal in the opposite direction. May be used.

[0020]

As described above, according to the present invention,
It is possible to provide an optical parallel transmission apparatus capable of performing automatic optical output control for parallel data including burst signal data in an inexpensive and simple optical mounting mode, which is extremely useful.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment.

FIG. 2 is a block diagram showing a second embodiment.

FIG. 3 is a waveform explanatory diagram illustrating an operation of a pulse width modulation circuit.

FIG. 4 is a block diagram showing a first conventional example.

FIG. 5 is a block diagram showing a second conventional example.

[Description of Reference Signs] 100, 101, ..., 10N Optical Fibers 110, 111, ..., 11N Driving Circuits 120, 121, ..., 12N Semiconductor Lasers 130, 131, ..., 13N Amplifier Circuits 140 , 141, ..., 14N Light receiving element 150, 151, ..., 15N Discrimination circuit 160 Average value detection circuit 161,162 Reception level detection circuit 165 Pulse width detection circuit 170,171 Bias current control circuit 180 Pulse width modulation circuit 190 peak value detection circuit 195 light receiving element 300 transmission line 310 multiplexed signal generator 320 transmitter 330 receiver 340 multiplexed signal decompressor 200, 201, ..., 20N optical fiber 210, 211, ..., 21N drive Circuits 220, 221, ..., 22N Semiconductor lasers 230, 231 ,. 23N amplifier circuit 240, 241, ..., 24N light receiving element 250, 251, ..., 25N identification circuit 260, 261, 262 average value detection circuit 265 pulse width detection circuit 270, 271 bias current control circuit 280 pulse width modulation Circuit 290 Peak value detection circuit 295 Light receiving element 400 Transmission line 410 Multiplex signal generator 420 Transmitter 430 Receiver 440 Multiplex signal restorer

Claims (2)

[Claims] 1. An optical parallel transmission apparatus for transmitting a signal by a plurality of optical channels including a synchronization signal transmission channel, and an optical receiving unit for detecting a reception level of the synchronization signal transmission channel, and an optical reception level of the synchronization signal transmission channel. Optical reception level information transmission means for transmitting information to the optical transmission side of the plurality of optical channels, and transmission levels of the plurality of optical channels according to the optical reception level information of the synchronization signal transmission channel transmitted to the optical transmission side. And a transmission level control unit for controlling the optical parallel transmission device. 2. A bidirectional optical parallel transmission apparatus for transmitting a signal by a plurality of optical channels including a synchronization signal transmission channel, wherein intensity information of an optical signal propagating through a transmission line is superimposed on a reverse direction synchronization signal for transmission and reception. An optical parallel transmission device, comprising: a synchronization signal transmission channel transceiver for transmitting; and a transmission level control unit that controls transmission levels of the plurality of optical channels according to intensity information of the optical signals.