JPS6374222A - Semiconductor optical transmitter - Google Patents

Abstract

PURPOSE:To eliminate a problem of the reliability of a Peltier element by controlling the temperature of a semiconductor laser by the Peltier element when a spectral half value width or peak wavelength of a monitor light of the semiconductor laser is at the outside of preset range in advance by the temperature change so as to reduce the operating time of Peltier element. CONSTITUTION:One of a rear face light 21 of the semiconductor laser LD1 branched by a half mirror 5 is received by a photo diode PD 3 and an APC circuit 10 controls a drive current of the LD 1 so as to make an output current of the PD 3 constant. The spectral half value width DELTAlambda is measured from the other of the light 21 by an optical spectrum analyzer 6 and the value is outputted digitally to a temperature control section 7. The temperature control section 7 controls the peltier element 4 to control the temperature of the LD 1 when the output of the optical spectrum analyzer 6 is at the outside of the preset range due to the temperature change thereby controlling the output of the optical spectrum, analyzer 6 within the preset range. Thus, the spectral half value width DELTAlambda does not exceed the allowable value and the drive time of the Peltier element 4 is decreased to reduce the load.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor optical transmission device suitable for long-distance, large-capacity optical communication.

[Conventional technology]

Semiconductor lasers (hereinafter abbreviated as LD) are generally used with a constant output (for example, 5 mW), but because the temperature dependence of the threshold current is significant, temperature fluctuations (heat sink temperature fluctuations), the light output fluctuates significantly. Therefore, in actual use, the LD
P C (Auto+aticPower Con
(trol) circuit or ATC (automatic
In most cases, it is used with an eTeo+perature control) circuit.

FIG. 3(a) is a block diagram showing a semiconductor optical transmission device having an APC circuit described in, for example, a general catalog of InGaAsPLD, and FIG.
1 is a block diagram showing a semiconductor optical transmission device having an ATC circuit described in Technical Report 1θ85, Volume 38 (No. 2), Page 86. FIG.

In these figures, 1 is of the Fabry-Perot type (F-P
2 is a heat sink, and 3 is a monitor photodiode (hereinafter referred to as monitor PD) that receives the backside light of the LD1.
), 4 is a Bertier element, 1o is an A20 circuit, 11
is the ATCu path, 2° is the front light of the LDI, and 21 is the back light (monitor light) of the LDI.

Next, each operation will be explained.

In the configuration shown in FIG. 3(a), even if the ambient temperature fluctuates, the temperature of the heat sink 2 fluctuates, and the threshold current of the LDI fluctuates, the light reception output of the monitor PD 3, that is, the intensity of the back surface light 21, remains constant. As such, the APC circuit 10 controls the drive current of LD1. In the F-P type LDI, output light is emitted from both cleavage planes, that is, front light 2o and back light 21.
The strength of is proportional. Therefore, during operation of the APC circuit 1o, the intensity of the front light 20 (which is generally used as the input light to the optical fiber) is also constant (e.g. 5 m
W) is maintained.

In the configuration of FIG. 3(b), the ATC@path 11 is configured such that the threshold current of LDl does not change even if the ambient temperature changes.
The current value flowing through the Vertier element 4 is controlled so that the temperature of the heat sink 2 detected by the thermocouple or thermistor becomes a constant value (for example, room temperature). Therefore, for example, when the intensity of the front light 20 is 5 rnW at room temperature, the threshold current of LD1 remains constant even if the ambient temperature changes, and the intensity of the front light 20 remains constant at 5 mW.

In a constant output state, F-1) type LD for optical communication
The spectrum of 1 generally has a shape as shown in FIG. 4(a), with several longitudinal modes.

At chamber Q and 5 mW output, the spectral half-width Δλ (the spread of the spectrum with an intensity of 172 of the peak wavelength) is 2.
~3 nm.

[Problem that the invention seeks to solve]

In the conventional semiconductor optical transmission device as described above, LDl is A
When a PC is driven, the operating current (current value that provides a constant optical output, for example, 5 mW output) changes with temperature, so as shown in Figure 5, the spectral half-width Δλ suddenly increases at a certain temperature (current). There is. Figure 4(b),
(C) shows the spectrum shape at point b and point 0 in FIG.

When the spectral half-width Δλ is large (as at point 0 in Figure 5), there is a large wavelength jump when the peak wavelength shifts to longer wavelengths as the temperature (current) rises, that is, there is a large jump in the number of longitudinal modes. This is often the case. Furthermore, when the temperature decreases, the spectral half-width Δλ may increase as shown at point d in FIG. 5.

In long-distance, high-capacity optical communications, if the wavelength spread of LDl, that is, the spectral half-width Δλ, is large, interference between signals will occur due to the dispersion characteristics of the optical fiber that is the transmission medium.
Transmission distance and modulation speed will be limited. number 10
For transmission of Km, 50 Mb/sec or more, the permissible value of the spectral half-width 2λ is several nanometers. If the allowable value is set to 4.
5nn, the spectral half-width Δλ exceeds the allowable value at the temperatures of points C' and d in FIG. Since the temperature of LD1 itself is constant, the operating current is also constant, and unless the spectral half width Δλ exceeds the allowable value at the fixed temperature, it cannot be used at the temperature of point 0 and point d in Figure 5. This problem does not arise. However, in general, driving the Beltier element 4 requires a large current on the order of amperes, and currently the lifespan (reliability) of the Beltier element 4 itself is not necessarily clear compared to that of the LDl. However, using this method had reliability problems.

The present invention has been made to solve these problems, and an object of the present invention is to provide a semiconductor optical transmission device that can prevent an abnormal increase in the spectral half-width.

[Means for solving problems]

The semiconductor optical transmission device according to the present invention includes a Vertier element for changing the temperature of a semiconductor laser, an optical spectrum analyzer for measuring the spectral half-width or peak wavelength of the monitor light of the semiconductor laser, and an optical spectrum analyzer for measuring the spectral half width or peak wavelength of the monitor light of the semiconductor laser. It is equipped with a temperature control section that controls the temperature of the semiconductor laser by driving a Vertier element when the temperature of the semiconductor laser falls outside the preset range due to a change, and keeps the output of the optical spectrum analyzer within the preset range. It is something that

[Effect]

In this invention, when the spectral half-width or peak wavelength of the semiconductor laser monitor light falls outside a preset range due to a temperature change, the temperature control section drives the Vertier element to control the temperature of the semiconductor laser. , the spectral half width or peak wavelength of the output light of the semiconductor laser is made to fall within a preset range.

〔Example〕

FIG. 1(a) is a block diagram showing an embodiment of a semiconductor optical transmission device of the present invention. In this figure, Figure 4 (a
) and (b) indicate the same parts, 5 is a half mirror, 16 is an optical spectrum analyzer, and 7 is a temperature controller.

Moreover, FIG. 1(b) is a block diagram showing an example of the structure of the temperature control section 7 in FIG. 1(a). In this figure, the same reference numerals as in Fig. 1(a) indicate the same parts, and 3
o is a computer for determining conditions; 31 is a D/A converter;
Reference numerals 32 and 33 are voltage comparison circuits (op-amp circuits M) to which reference voltages (not shown) corresponding to the permissible level of the spectral half-width Δλ are connected, and 34 and 35 are switching transistors.

Next, the operation will be explained.

First, one of the back lights 21 branched by the half mirror 5 is received by the monitor PD3, and the APC circuit 10 controls the drive current of the LD1 so that the output current of the monitor PD3 is constant. This is similar to the operation of the conventional APC circuit 10 shown in FIG. 3(a), but the other side of the branched back light 21 enters the optical spectrum analyzer 6,
Here, the spectral half-width 2λ is measured, and the value is digitally output to the temperature control section 7 (spectral half-width Δλ
The optical spectrum analyzer 6 that can output the value of
(There are models such as TQ-8345 manufactured by VANTEST). In the temperature control unit 7, a computer 3o for condition determination determines whether the spectral half-width 2λ increases as the temperature rises or becomes thicker as the temperature decreases.For example, in FIG. If it is in the state A, the computer 30 for condition determination uses the optical spectrum analyzer 6.
The output of 191. is directly converted to D/A. The voltage comparator circuit 32 compares the output of the D/A converter 31 with a reference voltage corresponding to the permissible level of the spectral half-width Δλ, and if the output of the D/A converter 31 is large, the voltage comparator circuit 32 34 is turned on, the Bertier element 4 is driven, and the temperature of the heat sink 2 is lowered.

In addition, when the condition is in the mouth state, the computer 30 for condition determination outputs the output of the optical spectrum analyzer 6 with a minus added to the D/A converter 31, and outputs the output of the optical spectrum analyzer 6 to the D/A converter 31.
7533 compares the output of the D/A converter 31 with a reference voltage, turns on the transistor 35 when the output of the D/A converter 31 is small, drives the Vertier element 4, and raises the temperature of the heat sink 2.

That is, in this invention, since the Bertier element 4 is driven so that the temperature of the heat sink 2 is, for example, between A and N in FIG. 5, the spectral half-value width Δλ does not exceed the permissible value, Since the driving time of the Beltier element 4 is short and the load is light, reliability problems are extremely reduced.

In the above embodiment, the optical spectrum analyzer 6 measures the spectral half width Δλ, and the voltage comparison circuits 32, 3
3 compares the spectral half-width Δλ with a reference voltage corresponding to its permissible level to drive the Bertier element 4, and the LDl
As described above, the temperature of the heat sink 2 is controlled by outputting the measured value of the peak wavelength ^ of the optical spectrum analyzer 6, and driving the Vertier element 4 depending on whether this is within the allowable range. It is also possible to control the peak wavelength λ by controlling λ.

FIG. 2 is a diagram showing the temperature dependence of the peak wavelength λ when outputting 5 mW. The peak wavelength and length of LDl, which has a peak in the 1300 nm band, generally exhibits a temperature dependence of about 0.4r+rn/°C. Therefore, in this case, in order to keep the peak wavelength length of LDI with peak wavelength λ = 1302 nm (point a) within the range of 1300±b at room temperature, the Peltier element 4 is operated at point b and point 0, and the heat sink 2 of LDl is operated. The temperature must be kept between about 7°C and about 32°C. [Effects of the Invention] As explained above, the present invention provides a method in which the spectral half-width or peak wavelength of the monitor light of a semiconductor laser is set in advance by temperature changes. Since the temperature of the semiconductor laser is controlled by a Peltier element when the temperature exceeds the specified range, the half-width or peak wavelength of the spectrum does not exceed the allowable value, making long-distance, high-capacity optical communication possible. Furthermore, since the operation time of the Peltier element is extremely short, there is an effect that there is no problem with the reliability of the Peltier element.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are block diagrams showing one embodiment of the semiconductor optical transmission device of the present invention and one embodiment of the structure of the temperature control section, and FIG. 2 is a diagram showing the temperature dependence of the peak wavelength. , FIGS. 3(a) and 3(b) are block diagrams showing a semiconductor optical transmission device having a conventional APC circuit and a semiconductor optical transmission device having a conventional ATC circuit, FIG. 4 is a diagram explaining the spectral half-width, FIG. 5 is a diagram showing the temperature dependence of the spectral half-width. In the figure, 1 is an LD, 2 is a sink, 3 is a monitor PD, 4 is a Peltier element, 5 is a half mirror, 16 is an optical spectrum analyzer, 7 is a temperature controller, and iQ is an APC.
In the circuit, 20 is a front light, and 21 is a back light. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masu Oiwa 1 (2 others) Figure 1 Figure 2 Figure 3 (a) ' (b) Figure 4 1300nm 300nm Figure 5 1 action (IC) Procedural amendment N (voluntary) Dear Commissioner of the Japan Patent Office ( 1. Indication of the case Japanese Patent Application No. 81-220229 2. Name of the invention: Semiconductor optical transmission device 3. Name of the person making the amendment 5. Column 6 for detailed explanation of the invention in the specification to be amended, Contents of the amendment ( 1) "rI nGaASPLD" on page 2, line 12 of the specification.
"Correct with Mitsubishi InGaAsP-LDJ. (2) 150 Mb/s also on page 5, line 11
ec'' is corrected to r500Mb/5ecJ. (3) Similarly, “Figure 4” on page 7, line 14, has been changed to “Figure 3”.
and correct it. that's all

Claims (1)

[Claims] A semiconductor optical transmission device configured to detect a monitor light of a semiconductor laser and control a drive current so that the output light of the semiconductor laser is constant, comprising: a Peltier element for changing the temperature of the semiconductor laser; an optical spectrum analyzer that measures the spectral half-width or peak wavelength of the laser monitor light; and an optical spectrum analyzer that drives the Peltier element to detect the semiconductor laser when the output of the optical spectrum analyzer goes outside a preset range due to temperature change. a temperature control unit that controls the temperature of the optical spectrum analyzer so that the output of the optical spectrum analyzer falls within the preset range.