Method and apparatus for measuring phase differences between intensity-modulated optical signals
US6429929B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 30, 2001 |
| Grant date | Aug 6, 2002 |
| Priority date | — |
| Expiry date | Mar 30, 2021 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01M11/333
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
In order to avoid errors inherent in the measurement of electrical phase differences or pulse arrival time in relative group delay measurements, different optical signals have their intensity modulated at a common high frequency and different permutations are selected. The amplitudes of corresponding electrical signals are detected and phase differences are computed on the basis of trigonometrical relationships. Because the modulation frequency is known, time differences can be deduced. Apparatus for measuring the phase differences conveniently comprises a slotted wheel (26) which passes selected ones or both of the optical signals. One of the optical signals may be split to produce a third signal with a predetermined phase shift, e.g. about 90 degrees at the modulation frequency and the amplitudes of some possible permutations of the three optical signals used to compute the phase difference. The measurements may be used to compute chromatic dispersion, polarization mode dispersion, elongation, and so on.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.