Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1996-02-27
1998-03-03
Negash, Kinfe-Michael
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
359161, 359183, H04B 1012
Patent
active
057241694
ABSTRACT:
A phase-modulated fiber optic communication link (9) with carrier signal filtering is disclosed. The phase-modulated fiber optic communication link (9) includes a laser (11) that produces a optical carrier signal that is conveyed by an optical fiber (13) to a phase modulator (15). A modulated RF signal phase modulates the optical carrier signal and produces a phase-modulated signal comprising a carrier component (27), an upper sideband (29), and a lower sideband (31). The upper and lower sidebands are out of phase by 180 degrees. The phase-modulated signal is conveyed by an optical fiber to a delay line filter (21). In one embodiment of the invention, the delay line filter (21) attenuates the power of the optical carrier signal and passes the sidebands substantially unattenuated. One of the sidebands is phase shifted by 180 degrees by the delay line filter. The output of the delay line filter is applied to a photodiode detector (23), which recovers the RF modulated signal. In an alternative embodiment of the invention, the delay line filter (76) divides the phase-modulated signal into two signals, each containing a part of the optical carrier signals and one of the sidebands. One of the two signals is phase shifted with respect to the other signal, whereby the sidebands contained in the two signals are in phase. The signals are applied to two photodiodes (88, 89) whose outputs are combined in a differential detector (90) resulting in the recovery of the RF modulated signal.
REFERENCES:
patent: 5373383 (1994-12-01), LaGasse
patent: 5432631 (1995-07-01), Mamyshev
Mark L. Farwell et al., "Increased Linear Dynamic Range by Low Biasing the Mach-Zehnder Modulator," IEEE Photonics Technology Letters, vol. 5, No. 7, Jul. 1993, pp. 779-782.
Daniel J. Fitzmartin et al., "Coherent Phase Modulation for Remote Antenna Applications," Photonics Systems for Antenna Applications Symposium, Monterey, California, Jan. 1991.
Norio Takato et al., "128-channel Polarization--Insensitive Frequency-Selection-Switch Using High-Silica Waveguides on Si," IEEE Photonics Technology Letters, vol. 2, No. 6, Jun. 1990, pp. 441-443.
K.J. Williams et al., "Observation of Photodetector Nonlinearities," Electronics Letters, vol. 28, No. 8, Apr. 9, 1992, pp. 731-732.
Negash Kinfe-Michael
The Boeing Company
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