Synchronous polarization and phase modulation using a periodic waveform with ...

(54) SYNCHRONOUS POLARIZATION AND

PHASE MODULATION USING A PERIODIC
WAVEFORM WITH COMPLEX HARMONICS
FOR IMPROVED PERFORMANCE OF
OPTICAL TRANSMISSION SYSTEMS

(75) Inventor: Neal S. Bergano, Lincroft, NJ (US)

(73) Assignee: Tyco Submarine Systems Ltd.,

Morristown, NJ (US)

( * ) Notice: Subject to any disclaimer, the term ol this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.

(21) Appl. No.: 08/580,869

(22) Filed: Dec. 29, 1995

(51) Int. C I. H04B 10 04

(52) U.S. CI 359/183; 359/158; 359/161;

359/181

Field of Search 359/158, 161,

359/180, 181, 183, 187

(58)

(56) References Cited

U.S. PATENT DOCUMENTS

4.965,857 10/1990 Auracher et al 455/618

5,107,358 4/1992 Hodgkinson et al 359/124

5,309,530 5/1994 Bergano et al 385/1

5,309,535 5/1994 Bergano et al 385/38

5,345,331 9/1994 Bergano et al 359/341

5.361,270 11/1994 Heismann 372/27

5,473,458 * 12/1995 Mamyshev et al 359/161

OTHER PUBLICATIONS

"Dual-Wavelength Data Transmitter for Reducing Facing in an Optical Transmission System", N. S. Bergano 10, Ser. No. 08/173288, filed Dec. 23, 1993.

A method and apparatus is provided that yields improved performance by modulating the optical phase and polarization ol an optical signal with a periodic waveform having harmonic content that is more complex than that associated with a simple sinusoidal waveform. A phase modulator receives an optical signal onto which data has been modulated at a predetermined frequency. The phase modulator modulates the phase ol the optical signal in a continuous manner with the periodic waveform with complex harmonics where the lundamental phase modulation frequency is equal to the same predetermined frequency at which the data is modulated onto the optical signal. In another illustrative embodiment ol the invention, a polarization modulator frxrther processes the optical signal by modulating the stateol-polarization ol the signal in a continuous lashion with the periodic waveform with complex harmonics where the fundamental polarization modulation frequency is equal to the same predetermined frequency at which the data is modulated onto the optical signal. In addition to being continuously modulated, the polarization modulation is performed so that the average value ol the state ol polarization over each modulation cycle is substantially equal to zero.

35 Claims, 4 Drawing Sheets