LIGHT SOURCE WAVELENGTH CONTROL APPARATUS

Abstract

Equipped between a transmitter 20 and an optical multiplexer module 25 of a division/multiplexer unit 24 are band-pass filters 23-1 through 23-m letting only a light of right wavelength pass while reflecting other wavelengths light. The transmitter 20 is equipped with a reflection light monitor 26 for monitoring a reflection light from the band-pass filters 23-1 through 23-m for examining an intensity of a reflection light. A wavelength of a light oscillated by a tunable laser diode (LD) unit 21 is controlled so as to make the intensity of the light smaller than a threshold value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a conventional WDM optical transmission apparatus;

FIG. 2 is a conceptual diagram of a configuration of a transmitter for use in a multiple wavelength WDM telecommunication system;

FIG. 3 is a diagram describing a problem associated with a conventional technique;

FIG. 4 is a diagram showing a fundamental comprisal of the present invention;

FIGS. 5A through 5C are diagrams exemplifying configurations of band-pass filters;

FIG. 6 is a diagram describing a three-port module used for FIG. 5C;

FIGS. 7A and 7B are diagrams describing a method for configuring a reflection light monitor by using a three-port module;

FIG. 8 is a diagram describing a method for equipping a three-port module according to a preferred embodiment of the present invention;

FIG. 9 is a diagram describing a problem associated with a wavelength adjustment;

FIG. 10 is a diagram describing a method for solving the problem shown in FIG. 9;

FIG. 11 is a flow chart showing a process sequence for setting a wavelength automatically;

FIGS. 12A and 12B are diagrams exemplifying a comprisal in the case of a variable optical attenuator existing between a transmitter and a multiplexer;

FIG. 13 is a flow chart of a wavelength setup process in the case of issuing an alarm in the event of a non-identicalness between a wavelength specified for a slot and that of a set wavelength;

FIG. 14 is a diagram describing a comprisal of equipping transmitters across a plurality of shelves and for setting wavelengths; and

FIG. 15 is a flow chart of a process in the case of setting wavelength across a plurality of shelves.

Claims

1. A light source wavelength control apparatus, comprising: a plurality of light sources;a multiplexer unit, which has a plurality of input ports, inputs lights from the plurality of light sources to the different input ports respectively and outputs a multiplexed light, and of which the plurality of input ports have mutually different transmissive wavelength characteristics;a plurality of reflection light generation units, being equipped at the previous stage of the respective input ports of the multiplexer unit, for allowing a pass or not allowing it according to the transmissive wavelength characteristics at the respective input ports corresponding to an incident light from a light source, specifically, allowing a pass if the incident light is a predetermined wavelength, or not allowing a pass if the incident light is other wavelengths; anda wavelength setup unit for setting an output wavelength of the corresponding light source as the predetermined wavelength for the reflection light generation unit by detecting a reflection light from the plurality of reflection light generation units.

2. The light source wavelength control apparatus according to claim 1, wherein said reflection light generation unit is a band-pass filter letting a predetermined light pass.

3. The light source wavelength control apparatus according to claim 2, wherein said reflection light generation unit utilizes a bulk type optical module.

4. The light source wavelength control apparatus according to claim 2, wherein said reflection light generation unit utilizes a Fiber Bragg Grating (FBG).

5. The light source wavelength control apparatus according to claim 2, wherein said reflection light generation unit utilizes a waveguide built-in type Fiber Bragg Grating.

6. The light source wavelength control apparatus according to claim 1, wherein said multiplexer unit utilizes a waveguide type module.

7. The light source wavelength control apparatus according to claim 1, wherein said reflection light generation unit is equipped between said light source and multiplexer unit.

8. The light source wavelength control apparatus according to claim 1, constituting said multiplexer unit and reflection light generation unit by three-port module which uses a spare port as a reflection light monitor-use port.

9. The light source wavelength control apparatus according to claim 8, wherein a multi-mode fiber is equipped on said reflection light monitor-use port of said three-port module.

10. The light source wavelength control apparatus according to claim 8, judging whether or not a light of the same wavelength as that of a wavelength to be multiplexed is included in a light transmitted from the previous stage by detecting a light appearing at the reflection light monitor-use port and generating an alarm if a light of the same wavelength is included therein in the case of constituting said multiplexer unit by a three-port module equipped with a reflection light monitor-use port.

11. The light source wavelength control apparatus according to claim 1, further comprising: an attenuation unit for attenuating a light incident to said multiplexer unit when a wavelength becomes a predetermined wavelength while said wavelength setup unit sets a wavelength.

12. The light source wavelength control apparatus according to claim 11, wherein said attenuation unit is an optical attenuator.

13. The light source wavelength control apparatus according to claim 11, wherein said attenuation unit is accomplished by controlling an output of an external modulator at an output which is approximately 20 dB lower that that of said light source.

14. The light source wavelength control apparatus according to claim 1, which detects whether or not a wavelength set by said wavelength setup unit is different from a wavelength to be output at a slot into which said light source is inserted, andissues an alarm if the former is different from the latter.