JPS6125231B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stabilized light source used in fiber optic communications.

Optical fiber communications are being put into practical use, but in order to lay optical fibers and cables, and to manufacture and measure optical components such as connectors and switches, it is necessary to use a stabilized light source whose output optical power does not fluctuate over time or with temperature changes. is essential.

Conventionally, semiconductor light emitting elements such as light emitting diodes (hereinafter referred to as LED) and semiconductor lasers (hereinafter referred to as LD) have been used as this type of light source. The output optical power of such a light source is stabilized by monitoring a portion of the output light, and when the output optical power changes due to a temperature change, a signal corresponding to the variation is negatively fed back to the light source. FIG. 1 is a diagram showing such a conventional light source. In the figure, light 12 from a light emitting element 11 is split into output light 14 and monitoring signal light 15 by an optical branch 13.
is guided to the photoreceiver 16. The output electric signal of the light receiver 16 is compared with a reference value in the drive circuit 17, and an output that compensates for the difference is sent from the drive circuit to the light emitting element 1.
Give to 1. However, such a stabilized light source
This method requires the optical branch 13 and the optical receiver 16, making the configuration complicated, and has the disadvantage that the output of the light emitting element 11 is attenuated by the insertion loss of the optical branch 13.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a stabilized light source having a simple structure and sufficient stability.

The stabilized light source of the present invention is characterized by comprising a semiconductor light emitting element such as an LD or an LED, and a constant current circuit having temperature dependence as a driving circuit for the light emitting element. With such a configuration, the output optical power can be stabilized over time and temperature changes.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 2 is a circuit diagram showing one embodiment of the present invention. In FIG. 2, reference numeral 21 is a silicon diode whose terminal voltage varies depending on temperature. An operational amplifier 22, a transistor 23, and a resistor 24 constitute a constant current circuit. The output current of the constant current circuit is given to the LED 25.

Now, if the temperature is constant, the terminal voltage of the diode 21 is constant and a constant current flows through the LED 25. Therefore, the output optical power of the LED does not change over time. Then when the temperature changes,
The terminal voltage of diode 21 changes, and LED 25
The current flowing through changes accordingly. By determining the terminal voltage-temperature characteristics of the diode 21 so that the change in the LED current caused by the temperature change in the terminal voltage of the diode 21 cancels out the change in the output optical power of the LED due to the temperature change, the LED The output optical power of can be kept constant despite changes in temperature. Furthermore, if the diode 21 is selected appropriately, it is possible to provide the diode 21 with the opposite characteristic, such that the output optical power increases as the temperature rises.

The stabilized light source shown in Figure 2 has output power fluctuations within 0.02 dB over an 8-hour period, and output power fluctuations when the ambient temperature changes from 0 to 50 degrees Celsius.
It was below 0.02dB. This stability is comparable to that of a light source using a conventional feedback circuit.

FIG. 3 shows stability data based on the example. Compared to constant current drive, the fluctuation range was suppressed to one-twentieth.

As described above, since the stabilized light source according to the present invention is constituted by a constant current circuit having temperature dependence, it does not require complicated and expensive components such as optical branches and receivers, and has a sufficiently high cost. It has great effects such as improving stability.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional stabilized light source, Figure 2 is a circuit diagram showing a conventional stabilized light source.
FIG. 3 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is a diagram showing the temperature characteristics of the stabilized light source according to the present invention and the temperature characteristics during constant current driving. 1 and 2, 11... light emitting element, 12... light, 13... optical branch, 14... output light, 15... signal light, 16... light receiver, 17...
Drive circuit, 21...Silicon diode, 22...
...Operation amplifier, 23...Transistor, 24...
Resistor, 25...LED.

Claims (1)

[Claims] 1. A semiconductor light-emitting element such as a light-emitting diode, a drive circuit that supplies a drive current to the light-emitting element, a first signal generating means that generates a first signal proportional to the drive current of the light-emitting element, and the light-emitting element. second signal generating means for generating a signal that compensates for changes in optical output due to temperature; and receiving the first signal at one terminal and receiving the second signal at the other terminal to control the drive circuit. 1. A stabilized light source comprising: a differential amplifier that generates a control signal for;