Coherent optical communication system with FSK heterodyne or hom

Details Coherent optical communication system with FSK heterodyne or hom Coherent optical communication system with FSK heterodyne or hom

1984-11-14

1988-07-19

Griffin, Robert L.

Telecommunications

Receiver or analog modulated signal frequency converter

Signal selection based on frequency

375 88, 375 91, 455608, 455611, 455619, H04B 900

Patent

active

047590807

ABSTRACT:
A laser (21) is frequency modulated by an electrical modulating signal of a bit rate into a modulated signal of a first and a second modulated frequency. A combination of an optical mixer (27) and an optical detector (31) carries out optical heterodyne or homodyne detection on the modulated optical signal to produce a detected signal having a first and a second frequency component. A component separator (32) is for selecting only one of the components from the detected signal. A detector (33) detects the selected component to produce a demodulated electrical signal representative of the modulating signal. The laser is preferably a semiconductor laser. More preferably, the semiconductor laser is frequency modulated after the modulating signal is converted to a current of an mBnB code sequence. When the bit rate is below and above about 10 Mbit/second, either the modulating signal or the mBnB code sequence current is preferably used in frequency modulating the semiconductor laser after caused to pass through a high-pass and a low-pass filter, respectively.

REFERENCES:
patent: 3383600 (1968-05-01), Calfee
patent: 3699445 (1972-10-01), Kinsel
patent: 4009385 (1977-02-01), Sell
patent: 4149071 (1979-04-01), Nagai et al.
patent: 4443890 (1984-04-01), Gomurian
patent: 4533874 (1985-08-01), Fischer
Favre-"Future Heterodyne-Type"-European Conf on Optical Comm., Sep. 8-11, 1981-Copenhagen, Denmark-4 pages.
Takasaki et al.-"Line Coding Plans"-Conf. Rec., vol. II, Intern. Conf. on Comm., San Francisco, Calif.-Jun. 16-18, 1975, pp. 32-20-32-24.
Saito et al., "S/N and Error Rate Evaluation for an Optical FSK-Heterodyne Detection System Using Semiconductor Lasers", IEEE Journal of Quantum Electronics, vol. QE-19, No. 2 (Feb. 1983), pp. 180-193.
Yamamoto, Yoshihisa, IEEE Journal of Quantum Electronics, "Receiver Performance Evaluation of Various Optical Modulation-Demodulation Systems in the 0.5-10 m Wavelength Region", vol. QE-16, No. 11, Nov. 1980, pp. 1251-1259.

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