JPH02132930A - Light output switching system - Google Patents

Abstract

PURPOSE:To obtain a inexpensive light output part switching circuit by combining two light outputs by use of an optical multiplexer, and switching two sports of the detected current of a PIN photodiode and the output of automatic output control circuit when the lowering of the light output of a live side is detected. CONSTITUTION:When the laser diode 1b of the living side package LD1 of an optical transmission part circuit deteriorates, and the light output begins to be lowered, the value of a current flowing in the PIN photodiode 1a which was constant at normal time begins to decrease. Then, when it falls lower than the set value of a comparator 7, the output polarity of the comparator 7 is inverted, and switches 6a and 6b are changed over to a spare side packaged LD2. Accordingly, the base terminal of the current source transistor 3c of the live side package LD1 is opened, and the live side package LD1 ceases to operate. Since the output of an optical transmission part is the sum of the light outputs of the packages LD1 and LD2 taken by the optical multiplexer 8, the constant light output can be transmitted even after switching.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical output switching system for an optical transmitter circuit using a laser diode as a light source.

[Conventional technology]

Conventionally, optical transmission circuits have been switched by using two lines, a working line and a protection line, and detecting an abnormality in the optical input signal on the receiving side and switching to the protection line.

[Problem that the invention attempts to solve]

In the conventional switching method described above, the optical transmitter and the optical receiver are divided into two parts.
Not only does this require two sets of transmission lines, but it also requires two transmission lines, which poses a problem in that it costs more than one system. Furthermore, when duplicating only the optical transmitter, there is a problem in that it is necessary to prepare two sets of the same package.

[Means to solve the problem]

The optical output switching method of the present invention includes two sets of laser diodes including a PIN photodiode, two sets of drive circuits that drive these two sets of laser diodes, and detects the current flowing through the PIN photodiode to switch the laser diode. In the optical transmitter circuit, which is composed of an automatic output control circuit that keeps the optical output constant, an optical multiplexer, and first and second switching devices, data signals are input to the two sets of drive circuits. Furthermore, two sets of optical outputs are combined by the optical multiplexer, and the configuration is such that only one laser diode is always operating, and the optical output of the operating laser diode is reduced. At this time, the detection current output of the PIN photodiode and the output of the automatic output control circuit are switched to the other laser diode side by the switch.

[For production]

In the present invention, P
IN Two sets of laser diodes including a photodiode and a structural circuit are mounted, so that only one side of the laser diode is always working, one is used for the current use and the other is used as a backup, and the two are connected using an optical multiplexer. The optical outputs of the two sets are combined, and when a decrease in the optical output on the working side is detected, the detection current of the PIN 7 autodiode and the output of the automatic output control circuit are switched.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

The figure is a circuit configuration diagram showing an embodiment of the present invention.

In the figure, 1m. 2a is PIN photodiode,
1b and 2b are laser diodes, and 3a to 3c and 43 to 4c are transistors, which constitute two sets of drive circuits that drive the laser diodes 1b and 2b. 5 is PIN photodiode 1m, 2a K
An automatic output control circuit detects the flowing current and keeps the optical output of the laser diodes 1b and 2b constant, 6m and 6b are switching devices, 7 is a comparator that detects a decrease in optical output and outputs a switching control signal, and 8 is a Optical multiplexer, 9 is an optical output terminal, 10a,
10b is a data signal input terminal. (2) cc indicates a power supply, and DATA and DATA indicate a data signal.

The data signal is input to two sets of drive circuits, and the optical outputs of the two sets are further coupled by an optical multiplexer 8, so that only one laser diode is always in operation. PIN photodiode detection 'I' occurs when the optical output of the laser diode on the side
A switch 6a switches the IK output and the output of the automatic output control circuit 5.
, 6bK are configured to switch to the other laser diode side.

Next, the operation of the embodiment shown in this figure will be explained.

First, in general, laser diodes are driven by adding a DC bias current to the modulation current, and then controlling the optical output by changing the DC bias current.However, the laser diode in the example shown in this figure The drive circuit uses a method of controlling the optical output by changing the amplitude of the modulation current without using a DC bias current.

Here, the left laser diode 1b and PIN7 autodiode 1a are set to L[)! , right laser diode 2b
and pIN 7 Let the autodiode 2a be LDt, and LD
If l is the active side (LD2 is the standby @), under normal conditions, the switch 6a switches υLD. The side PIN photodiode 1a is connected to the automatic output control circuit 5, and the switch 6b K
The output of the automatic output control circuit 5 is connected to the current source transistor 3c of the LD+111. Therefore, the data signals from the data signal input terminals 10a and 10b are input to two sets of drive circuits, and the transistors 4a to 4
Since the base terminal of the current source transistor 4c of the drive circuit on the standby side constituted by the switch 6b is set to an open trap by the switch 6b, the LD on the standby side does not operate.

Next, when the working laser diode 1b deteriorates and its optical output begins to decrease, the PIN, which was constant during normal operation, changes.
The value of the current flowing through the photodiode 1a also begins to decrease. When the current value of the comparison aT is lower than the set current value, the polarity of the output of the comparator 7 is reversed, and the polarity of the output of the comparator 7 is reversed, and the switch 6a and the switch 6b
is LD. Switch to the side. Therefore, this time LD,91
If the base terminal of the current source transistor 3c of No. 11 is open, LQ on the current side will not operate.

However, since the optical transmitter output is the sum of the optical outputs of the optical multiplexer 8K and LD, it is possible to send out a constant optical output even after switching.

〔Effect of the invention〕

As explained above, the present invention mounts two sets of laser diodes including a PIN photodiode and a driving circuit in the same package of an optical transmitter, so that only one laser diode is always operated, and one is used for current use while the other is used. is used as a backup, and the two sets of optical outputs are combined using an optical multiplexer to detect a decrease in the optical output on the working side.
Photodiode detection 1! Since the optical output can be switched by switching between the current and the automatic output control circuit output, it is possible to realize a very inexpensive switching circuit for the optical output section.

[Brief explanation of the drawing]

The figure is a circuit configuration diagram showing an embodiment of the present invention. 1a, 2 breath fist●ψ●PIN photodiode, 1b.
2b ●●●● Laser diode, 3a to 3c, 4a
~4c ●●●φ transistor, 5●●●●self-operated output control circuit, 6a, 6b ●9●● switch, T/comparator,

Claims (1)

[Claims] Two sets of laser diodes including a PIN photodiode, two sets of drive circuits that drive these two sets of laser diodes, and an automatic output that detects the current flowing through the PIN photodiodes and keeps the optical output of the laser diodes constant. In an optical transmitter circuit composed of a control circuit, an optical multiplexer, and first and second switching devices, a data signal is input to the two sets of drive circuits, and two sets of optical outputs are input. The laser diodes are coupled by the optical multiplexer, and are configured such that only one laser diode operates at any time, and when the optical output of the operating laser diode decreases, the detected current output of the PIN photodiode and An optical output switching system characterized in that the output of the automatic output control circuit is switched to the other laser diode side by the switching device.