Monitoring of a laser source with front and rear output photodetectors to determine frontal laser power and power changes over laser lifetime
US8971362B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 12, 2010 |
| Grant date | Mar 3, 2015 |
| Priority date | — |
| Expiry date | Aug 9, 2031 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01S5/4025
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A power monitoring and correction to a desired power level of a laser or group of lasers utilizes two photodetectors which are employed to accurately determine the amount of output power from the front end or “customer” end of a laser or a plurality of such lasers. During power detection, which may be accomplished intermittently or continuously, the laser is modulated with a tone of low frequency modulation. One photodetector at the rear of the laser is employed to detect the DC value of the frequency tone, i.e., a value or number representative of the AC peak-to-peak swing, amplitude or modulation depth of the tone. Also, the rear photodetector may be employed to determine the optical modulation index (OMI). In either case, these values may be employed in a closed loop feedback system to adjust or otherwise calibrate the value of the low tone frequency relative to the total desired bias current applied to the laser. A front photodetector is employed to receive a portion of the total output of the laser, or of each laser, and the average output power of the laser, or of each laser, is determined from already knowing the optical modulation index (OMI) via the rear photodetector. Thu…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.