356 0 Thursday Afternoon OFC '98 Technical Digest U I I I I I Optical Input I ONU module i, Electrical 'output ThT4 Fig. 2. Small ONU module for FM converted multichannel video signal transmission systems: (a) schematic block diagram; (b) photograph. Width 27 mm, height 10 mm, depth 18 mm. existing TV tuners. Because the wiring for high frequency signals is reduced in the proposed module, the cost can be reduced. Figure 3 shows the carrier-to-noise ratio (CNR), composite secondorder (CSO)

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... tion, and composite triple beat (CTB) versus number ofAM video channels. Received optical power was adjusted to -15 dBm, and pre-distortion circuits were used to compensate for CSO and CTB. Compare with conventional AM-SCM systems without FM conversion: CNR is improved by >4.8 dB. As the number ofvideo channels increases, 55 50 8 B m 5 2 45 0 oc z 0 40 35 Cpnventi nal AMS.CM \ without F h conversion lated) I I I I I \ Cpnventi nal AMS.CM k c u l a t without F h conversion ed) 15 20 25 30 35 40-45 Number of AM video channel ThT4 Fig. 3. CNR, CSO, CTB vs. number of AM video channel. Received optical power is -15 dBm. Measured frequency is at worst case channel. Predistortion circuits are used for CSO and CTB compensation. Frequency deviation are 173, 148, 114 MHzO-pich for 20, 30, 40 AM video channel transmission, respectively. The linewidth of FM laser and local laser are 150 and 17.9 kHz, respectively. the CNR are degraded because the frequency deviation must be reduced. Therefore, the linear range of the demodulator should exceed 5.5 GHz to improve the CNR. On the other hand, the degradation of CSO and CTB is due to the nonlinearity of the demodulator caused by group delay of the limiting amplifier and so on. In conclusion, we have proposed a small ONU module for FM converted multichannel video signal transmission systems, and demonstrated multichannel video signal transmission.