Optical transmitter, wavelength alignment method, and passive optical network system

Patent metadata

Field	Value
Publication number	US-9628192-B2
Application number	US-201514924344-A
Country	US
Kind code	B2
Filing date	Oct 27, 2015
Priority date	Oct 30, 2014
Publication date	Apr 18, 2017
Grant date	Apr 18, 2017

Abstract

Embodiments of the present invention disclose an optical transmitter, a 10 G-DML, an MPD 1 , an MPD 2 , a collimation lens, and a narrowband optical filter are disposed in a TO to achieve monitoring of an optical power, received optical powers are monitored by using the MPD 1 and the MPD 2 , the detected optical powers are output to a wavelength locking monitoring circuit by using a TO pin, variations, which are detected by the wavelength locking monitoring circuit, of the optical power and a variation of a wavelength locking factor K0 are separately compared with corresponding thresholds, and a comparison result are sent to a wavelength locking control circuit, to enable the wavelength locking control circuit to adjust, according to the comparison result and by using the TO pin, a temperature of a TEC to perform wavelength alignment.

First claim

What is claimed is:

1. An optical transmitter, comprising:
a transmitter optical (TO) base, a thermoelectric cooler (TEC), and a heat sink that are transverse and are connected sequentially from bottom to top;
a second monitor photodiode detector (MPD), a 10 G-directly modulated laser (G-DML), a collimation lens, and a narrowband optical filter that are disposed above the heat sink, wherein the second MPD and the collimation lens are located at two sides of the 10 G-DML, and the narrowband optical filter is located at one side of the collimation lens, and one surface, which faces the collimation lens, of the narrowband optical filter is connected to the heat sink at a preset tilt angle;
a first MPD disposed above the narrowband optical filter;
a wavelength locking monitoring circuit connected to a TO pin disposed at one side of the TO base, and a wavelength locking control circuit connected to the wavelength locking monitoring circuit;
wherein a forward emitted light emitted by the 10 G-DML is input to the narrowband optical filter through the collimation lens, and the narrowband optical filter splits the forward emitted light into a forward transmitted light and a backward reflected light, transmits, at a preset elevation angle, the backward reflected light to the second MPD, and partially reflects the forward transmitted light to the first MPD connected to the narrowband optical filter;
wherein the first MPD is configured to receive and monitor a first optical power of the forward transmitted light, and the second MPD is configured to receive and monitor a second optical power that is after the backward emitted light and the backward reflected light complement each other; and
wherein the wavelength locking monitoring circuit is configured to receive the first optical power and the second optical power by using the TO pin, separately compare detected variations of the first optical power and the second optical power and a variation of a wavelength locking factor K0 with corresponding thresholds, and send a comparison result to the wavelength locking control circuit, to enable the wavelength locking control circuit to adjust, according to the comparison result and by using the TO pin, a temperature of the TEC to perform wavelength alignment, wherein the wavelength locking factor K0 is a ratio of the first optical power to the second optical power or a difference between the first optical power and the second optical power.

2. The optical transmitter according to claim 1 , wherein the wavelength locking monitoring circuit is configured to:
when the variations of the first optical power and the second optical power and the variation of the wavelength locking factor K0 exceed the corresponding thresholds, compare the first optical power with a first optical power detected last time, and compare the second optical power with a second optical power detected last time, and if the first optical power is less than the first optical power detected last time, and the second optical power is greater than the second optical power detected last time, obtain a first comparison result, and send the first comparison result to the wavelength locking control circuit; otherwise, obtain a second comparison result, and send the second comparison result to the wavelength locking control circuit, wherein the first comparison result is that wavelengths of the forward emitted light and the backward emitted light that are emitted by the 10 G-DML drift towards a longer wave, and wherein the second comparison result is that wavelengths of the forward emitted light and the backward emitted light that are emitted by the 10 G-DML drift towards a shorter wave.

3. The optical transmitter according to claim 2 , wherein the wavelength locking control circuit is further configured to:
when the first comparison result is received, send, by using the TO pin, an instruction for reducing the temperature of the thermoelectric cooler TEC, and control a wavelength of the 10 G-DML to be aligned with the wavelength locking factor K0; or
when the second comparison result is received, send, by using the TO pin, an instruction for increasing the temperature of the TEC, and control a wavelength of the 10 G-DML to be aligned with the wavelength locking factor K0.

4. A wavelength alignment method for use with an optical transmitter, the method comprising:
receiving, by a wavelength locking monitoring circuit by using a transmitter optical (TO) pin, a first optical power, which is monitored by a first monitor photodiode detector (MPD), of a forward transmitted light, and a second optical power that is monitored by a second MPD and that is after a backward emitted light and a backward reflected light complement each other, and using a ratio of the first optical power to the second optical power or a difference between the first optical power and the second optical power as a wavelength locking factor K0;
monitoring, by the wavelength locking monitoring circuit, whether variations of the first optical power and second optical power and a variation of the wavelength locking factor K0 exceed corresponding thresholds; and
when the variations of the first optical power and the second optical power and the variation of the wavelength locking factor K0 exceed the corresponding thresholds, comparing the first optical power with a first optical power detected last time, comparing the second optical power with a second optical power detected last time, sending a comparison result to a wavelength locking control circuit, and adjusting, by the wavelength locking control circuit, according to the comparison result and by using the TO pin, a temperature of a thermoelectric cooler (TEC) to perform wavelength alignment.

5. The method according to claim 4 , before receiving, by a wavelength locking monitoring circuit by using a TO pin, a first optical power, which is monitored by a first MPD, of a forward transmitted light, and a second optical power that is monitored by a second MPD and that is after a backward emitted light and a backward reflected light complement each other, the method further comprises:
reading, by the wavelength locking monitoring circuit, a temperature of the TEC at a standard working point, a first standard optical power M1 of the first MPD, and a second standard optical power M2 of the second MPD, calculating an average optical power (Pa) with t*M1+M2 in a preset effective wavelength region, and using the calculated Pa as input of an automatic optical power control loop, wherein an input end of the automatic optical power control loop is connected to the first MPD or the second MPD, and t is a preset proportion coefficient.

6. The method according to claim 4 , wherein comparing the first optical power with a first optical power detected last time, comparing the second optical power with a second optical power detected last time, sending a comparison result to the wavelength locking control circuit, and adjusting, by the wavelength locking control circuit, according to the comparison result and by using the TO pin, a temperature of a thermoelectric cooler (TEC) comprises:
comparing the first optical power with the first optical power detected last time, and comparing the second optical power with the second optical power detected last time;
if the first optical power is less than the first optical power detected last time, and the second optical power is greater than the second optical power detected last time, obtaining a first comparison result, wherein the first comparison result is that wavelengths of a forward emitted light and a backward emitted light that are emitted by a 10 G-directly modulated laser (G-DML drift towards a longer wave;
sending the obtained first comparison result to the wavelength locking control circuit, to enable

Assignees

• Huawei Tech Co Ltd

Inventors

• Liao Zhenxing
• Wang Lingjie
• Zhou Min
• Huang Jing

Classifications

• H01S5/00

  Semiconductor lasers (superluminescent diodes H10H20/00) · CPC title

• H04B10/572 Primary

  Wavelength control · CPC title

• H01S5/02415

  by using a thermo-electric cooler [TEC], e.g. Peltier element · CPC title

• H01S5/0687

  Stabilising the frequency of the laser · CPC title

• H01S5/02212

  Can-type, e.g. TO-CAN housings with emission along or parallel to symmetry axis · CPC title