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Proceedings Paper

Broadband receiver-based distortion elimination in phase-modulated analog optical links using four-wave mixing
Author(s): Amit Bhatia; Hong-Fu Ting; Mark A. Foster
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Paper Abstract

We present a method for full distortion elimination in phase-modulated analog optical links using the nonlinear optical process of four-wave mixing (FWM). Phase-modulated links consist of a laser and phase modulator in the transmitter and an interferometer (or local oscillator) and photodiode in the receiver. Phase modulation is a linear process, so distortion is introduced in the interferometric detection process. Quadrature biasing eliminates even-order distortion products, leaving only odd-order distortion. Here we introduce a method for eliminating these odd-order distortion products in the receiver. A small portion of the phase-modulated signal is tapped and combined with an unmodulated CW laser to seed a cascaded FWM comb source. This process generates an array of lightwaves with integer multiples of the signal’s phase modulation. By suitably scaling and combining these lightwaves with the original signal the overall transfer function of the interferometric receiver can be linearized (or given another tailored shape) through a Fourier synthesis approach. By combining a single lightwave from the generated comb with the original signal, we demonstrate the complete elimination of third-order distortion from the phase-modulated link leaving fifth-order distortion as the dominate source of distortion. We show a 17.6-dB SFDR improvement (1-Hz bandwidth) for a 6 GHz link operating at 5-mA total photocurrent and a 16.4-dB SFDR improvement (1-Hz bandwidth) for a 15 GHz link operating at 10-mA total photocurrent. By appropriately combining additional lightwaves from the generated comb, higher-order distortion products can be eliminated to produce an ideal linear (or custom shaped) transfer function.

Paper Details

Date Published: 14 March 2015
PDF: 6 pages
Proc. SPIE 9362, Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications VIII, 936213 (14 March 2015); doi: 10.1117/12.2079807
Show Author Affiliations
Amit Bhatia, Johns Hopkins Univ. (United States)
Hong-Fu Ting, Johns Hopkins Univ. (United States)
Mark A. Foster, Johns Hopkins Univ. (United States)

Published in SPIE Proceedings Vol. 9362:
Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications VIII
Laurence P. Sadwick; Tianxin Yang, Editor(s)

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