MULTICHANNEL AM VIDEO TRANSMISSION USING A HIGH-POWER ND - YAG LASER AND LINEARIZED EXTERNAL MODULATOR

A high-power Nd:YAG laser with a linearized external modulator-based system is demonstrated for a transmission of 50 channels of vestigial sideband amplitude modulated (VSB AM) video. The 1320 nm diode-pumped Nd: YAG laser is an attractive source for AM video transmission due to the high output power (~200 mW) and low relative intensity noise (< −170 dB/Hz). However, the required external modulator generates third-order distortion products, which limit the performance of such a system. In this paper, we demonstrate a predistortion linearization technique which reduces the modulator generated third-order distortion products by 16.4 dB, allowing a modulation index of 3.37% per channel. When combined with the Nd: YAG laser, this yields a 50-channel video transmission system with a 12 dB optical power budget for video carrier-to-noise ratios of 52 dB and composite distortion products (CSO and CTB) less than −60 dBc. The demonstrated power budget is sufficient to allow four-way power splitting, with the remaining margin comparable to the best results obtained with DFB laser-based AM transmission systems. © 1990 IEEE