France Telecom

France Telecom Etablissement Autonome De Droit Public

Orange

Daniel Hui Bon Hoa

Paulette Gavignet

Christian Dourthe

Erwan Pincemin

Andre Tromeur

Michel Condom

The differential group delay is measured in an optical fiber connection for an optical signal undergoing a phase modulation BPSK or DPSK by a digital signal at a given rate. A polarization controller at an emerging end of the connection scans polarization states of the modulated optical signal. An emulator iteratively introduces an additional delay in the modulated optical signal emerging from the connection and combines the delayed modulated optical signal and the non delayed modulated optical signal which are both polarized along two orthogonal axes into a resulting optical signal. A polarization controller and a fixed polarizer select a polarization state in the resulting optical signal along one of bisecting lines of the orthogonal axes into a linearly polarized signal. An eye diagram or a spectrum of the polarized signal is acquired by a digital oscilloscope or an optical spectrum analyzer to determine the differential group delay.

Measuring differential group delay in an optical fiber connection

Apparatus for measuring the differential group delay &#x3c4;in an optical fiber connection. The apparatus comprises at the inlet to said connection, a generator () for generating a binary signal sequence at a data rate D and a first polarization controller () suitable for subjecting the binary signal of an incoming sequence to a first scan through polarization states; and at the outlet from the connection, a second polarization controller () suitable for subjecting the signal resulting from the outgoing sequence to a second scan through polarization states, independently of said first polarization scan, a differential group delay emulator () suitable for introducing a variable additional group delay &#x3c4;, and an analyzer device () suitable for detecting the equality &#x3c4;+&#x3c4;=1/D in the resulting signal sequence.

Method of measuring the differential group delay of an optical fiber connection

A truncated frequency discriminator according to the present invention features an amplifier (A), phase adjustment circuits (CAP1, CAP2) and circuitry (V1, V2) for very weakly forward polarizing Schottky diodes (DS1, DS2). Such a truncated frequency discriminator allows for a reduced noise and may find particular application in optical telecommunications receivers.

Truncated frequency discriminator

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Lannion, France

Daniel Hui Bon Hoa