JPH03197909A - Laser diode module - Google Patents

Abstract

PURPOSE:To electrically correct the fluctuation in Pf by a change in ambient temp., i.e. tracking error to a min. by constituting a PD for correcting the tracking error and a circuit for correction within a module. CONSTITUTION:Reflected light 11 at the end of an optical fiber is detected by a photodiode 5 of a tracking error correcting circuit 6 and is fed back to a driving circuit of an LD. The PD 5 is previously set in the position where a photodetecting current is largest at the time when the incident power of the optical fiber is optimum, by which the change in the position of the reflected light 11 is detected together with a change in the incident power of the optical fiber when there is the ambient temp. change. The change rate of this time is negative-fed back to the driving system of the LD by the circuit 6 for correcting the tracking error, by which the Pf (Fiber output power) is maintained constant. The tracking error is corrected to the min. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light emitting device for optical communication, and particularly to a laser diode module for optical communication.

[Conventional technology]

The conventional laser diode module for optical communication is the third
As shown in the figure, a laser diode (LD) 1
A monitor photodiode (PD) 2, a lens/optical system 3 for focusing the light beam from the LD at the end of the optical fiber, and an optical fiber 4 are housed in one package (module housing) 10. However, in order to keep the fiber-coupled light output (Pf) constant under the same operating conditions against external stresses such as changes in ambient temperature, it is necessary to rely only on the mechanical stability of the package. The reliability of the module was also dominated by this.

[Problem to be solved by the invention]

The conventional laser diode modules mentioned above have only mechanical stability, especially against changes in ambient temperature, i.e.
There is a drawback in that the amount of tracking error has to be determined only based on the stability of the optical output (P'') due to the solder material and the material of the built-in components against thermal expansion and thermal contraction.

[Means to solve the problem□]

The laser diode module of the present invention includes conventional components such as an LD, a monitoring PD, an optical system, and an optical fiber, as well as a photodiode for tracking error correction, and a configuration for transmitting a signal from the photodiode to the LD drive system. In addition to conventional mechanical stability, changes in Pf are detected by the reflected light of the light beam at the input end of the optical fiber and electrically fine-tuned due to changes in ambient temperature. In addition, the configuration is such that tracking error (amount of change in Pf with respect to ambient temperature) can be accurately corrected.

〔Example〕

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

FIG. 1 shows the configuration of the present invention. Further, FIG. 2 shows a circuit block diagram. A light beam emitted from the LDl passes through an optical system and a lens system 3, and is housed in a package (module housing) 10 with a configuration in which the beam is substantially focused at the end of the optical fiber. At this time, by shaping the end face of the optical fiber 4 obliquely, the reflected light of the light beam at the end face of the optical fiber is prevented from returning to the LDI, reducing reflected light noise, and the tracking error of the reflected light 11 at the end face of the optical fiber is corrected. It is detected by the photodiode (tracking error correction photodiode) 5 of the circuit 6 and fed back to the LD drive circuit (not shown) (see Figure 2 for the circuit block diagram). is LDI
This is to monitor the output of the LDI and stabilize the output of the LDI.

If there is some variation in the thermal expansion of the package (module housing) 10 or the positional accuracy of the mounting of other components due to a change in ambient temperature, a coupling deviation of the laser beam 12 to the optical fiber 4 occurs. This also causes the incident power of the optical fiber to fluctuate. Furthermore, the state of the reflected light 11 also changes as the incident power changes. P at the position where the received current is maximum when the incident power of the optical fiber is optimal.
By setting D5, when there is a change in ambient temperature (ambient temperature surrounding the package), it is possible to detect a change in the optical fiber incident power, a change in the position of the reflected light 11, or a change in the reflected power itself. The amount of change at this time is negatively fed back to the LD system (not shown) by the tracking error correction circuit 6 shown in FIG. 2, thereby holding Pf (fiber out put power) constant.

〔Effect of the invention〕

As explained above, by configuring both the tracking error correction PD and the correction circuit in a module, the present invention has the effect of electrically correcting fluctuations in P'' caused by changes in ambient temperature, that is, tracking errors, to a minimum. be.

FIG. 3 shows a circuit block diagram of a conventional laser diode module.

1...Laser diode, 2...Monitor photodiode, 3...Optical system, 4...Optical fiber 5
... Photodiode, 6... Tracking error correction circuit, 10... Module housing (bunkage).

Claims (1)

[Claims] A laser diode (hereinafter abbreviated as LD), a monitor photodiode (hereinafter abbreviated as monitor PD) installed behind the LD, an optical fiber whose end face is cut diagonally, and an optical system (lens) for coupling the laser beam to the optical fiber. system), a tracking error detection photodiode (PD) for detecting changes in reflected light at the end of an optical fiber, and a tracking error correction circuit that amplifies the received signal and corrects the laser diode drive current in one package. A laser diode module that is characterized by being placed inside.