An Optical Bi-phase Modulator for Millimeter Wave Subcarrier Systems

Howard J. THOMAS  Nobuaki IMAI  Eiichi OGAWA  

IEICE TRANSACTIONS on Electronics   Vol.E79-C   No.1   pp.32-39
Publication Date: 1996/01/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Optomicrowave Techniques and Their Applications)
Category: Optomicrowave Devices
bi-phase modulator,  millimeter wave subcarrier systems,  optical modulator,  Mach-Zehnder external optical modulator,  

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This paper proposes a novel optical modulator for a millimeter wave (MMW) subcarrier optic link. The modulator enables the bi-phase modulation of MMW subcarriers. It simplifies the optic link by unifying such functions as IF modulation, up-convertion to MMW, and optical modulation, which are separately equipped in a conventional system. A simple model of a Mach-Zehnder external optical modulator (EOM) is used to illustrate how bi-phase modulation of millimeter wave (MMW) subcarriers can be accomplished by switching the EOM bias with a binary data signal. Experimental results are presented to confirm predictions. A wideband communications test system employing the EOM as a bi-phase modulator and utilizing spread spectrum modulation (1.3 µm optical wavelength, 40 GHz subcarrier, 100 MHz chip rate, 10MHz data rate) was developed. Bit error rate (BER) characteristics of an optical link that includes the proposed modulator are presented and compared with ideal performance and simulated predictions. Degradation of the BER characteristics from the simulation was less than 1 dB at a BER of 10-6. A frequency doubling subcarrier bi-phase modulator is also described.