Mixing interferometer used as a communications link
US5144468A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 16, 1989 |
| Grant date | Sep 1, 1992 |
| Priority date | — |
| Expiry date | Jun 16, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B10/64
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
An interferometer, such as a fiberoptic Mach-Zehnder type, is equipped at a transmission end of the system with a phase modulator driven by a data-input signal to be transmitted; and at a reception end with another phase modulator driven by a large reference signal. Nonlinear dependence of output intensity on these signals yields an intensity component that is the product of the signals at the modulators; and in turn an electrical output-signal component at frequency equal to the difference between the data- and reference-signal frequencies. A servocontrolled phase bias holds the system near a minimum in overall light level, where nonlinearity is prominent while intensity-related noise is minimized. The reference source and the bias are at the receiver end of the system, providing advantages: (1) the reference signal can be tuned manually or dynamically to optimize reproduction of the input signal, (2) the detector output can be mixed back up to the original data-input frequency using the same reference for mixing up as used optically for mixing down--eliminating frequency error and drift, and excess phase noise; and (3) only the modulators and purely optical elements need operate …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.