Broadband class-AB microwave-photonic link using polarization modulation

• Published in: IEEE photonics technology letters Vol. 18; no. 9; pp. 1073 - 1075
• Main Authors: Bull, J.D., Darcie, T.E., Jinye Zhang, Kato, H., Jaeger, N.A.F.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.05.2006; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Analog links; Broadband; Cancellation; Carriers; class-AB (CAB); Detectors; Distortion; Dynamic range; Electrooptic modulators; Electrooptics; intensity-noise suppression; Links; microwave-photonic links; Modulators; Noise cancellation; Noise reduction; Optical distortion; Optical modulation; optical modulator; Optical noise; Optical polarization; polarization modulator (PolM); polarization-mode converter; spur-free dynamic range (SFDR); Transfer functions
• ISSN: 1041-1135; 1941-0174
• DOI: 10.1109/LPT.2006.873356

A novel broadband class-AB (CAB) microwave-photonic link is demonstrated using an AlGaAs-GaAs electrooptic mode-converter-based polarization modulator (PolM). The polarization-modulated signal is split into two paths, each independently optically biased to provide two electrooptic transfer functions operating close to, but on opposing sides of, their nulls. Experimental results at 2 and 4 GHz confirm that detection of the transfer functions in a differential detector provides excellent cancellation of second-order distortion and recreates the same third-order distortion as a quadrature-biased Mach-Zehnder modulator. Biasing the operating points near the null reduces optical carrier power, and hence, carrier-related noise, thereby increasing achievable spur-free dynamic range. The use of the PolM allows the CAB link to be implemented with a single modulator, reducing the matching requirements of dual modulator schemes and allowing third-order distortion-limited broadband operation.