Control loop circuit and method therefor
US6829267B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 3, 2002 |
| Grant date | Dec 7, 2004 |
| Priority date | — |
| Expiry date | Sep 3, 2022 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B10/504
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
In an optical communications system, it is necessary to control the extinction ratio of a laser device (192) of an optical transmission unit. The laser device (192) is typically used to transmit a signal that can be approximated by a pseudo-random bit stream. The bit stream is monitored by collecting light from a back facet of the laser device (192) using a photodiode (194) in a control loop. Due to band limiting effects of the photodiode (194) and parasitic circuit track capacitances, a feedback signal generated by the photodiode (194) becomes distorted, leading to difficulties in controlling the extinction ratio. The present invention therefore provides an apparatus that simulates a signal generated by the photodiode (194) and subsequent processing of the photodiode signal. The simulated signal and the processed photodiode signal are compared so as to generate a control signal for controlling modulation amplitude of the laser device (192) and hence the extinction ratio.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.