Control of delay line interferometer
AssigneeLucent Technologies Inc.
InventorsHerbert Haunstein, Ralph Schlenk
Life of this patent
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Abstract
The delay setting of an optical delay line interferometer (DLI) used to decode differentially encoded phase shift keyed signals (DPSK or DQPSK) is controlled using a control signal representative of the ratio Perr2/Perr1 of the rate of occurrence of double errors and the rate of occurrence of errors. The ratio Perr2/Perr1, as the delay setting of the DLI is varied, exhibits a characteristic W-shaped structure consisting of a local maximum at the optimum value and two minima adjacent to the maximum, one on each side of it. This structure is present over a wide range of signal to noise ratio and residual dispersion.
Claims12
A method of controlling the delay setting of an optical delay line interferometer used to decode differentially encoded phase shift keyed signals, said method comprising:
- determining the rate of occurrence of errors Perr1 in the decoded signals;
- determining the rate of occurrence of double errors Perr2 in the decoded signals;
- deriving a control signal representative of the ratio Perr2/Perr1 of the determined rates;
- and
- using said control signal to control said delay setting.
Apparatus for controlling the delay setting of an optical delay line interferometer used to decode differentially encoded phase shift keyed signals, said apparatus comprising:
- means for determining the rate of occurrence of errors Perr1 in the decoded signals;
- means for determining the rate of occurrence of double errors Perr2 in the decoded signals;
- means for deriving a control signal representative of the ratio Perr2/Perr1 of the determined rates;
- and
- means for using said control signal to control said delay setting.
Dependencies are inferred from the claim text.