A practical 32-line photonic space-division switching system a fabricated using the world first 8x8 polarization independent LiNbO3 matrix switches. Owing to their polarization independence, the switching system can employ ordinary single-made optical fibers for subscriber access lines, which greatly contributes to make a photonic switching system practical and competent for broadband communications services. A three-stage switching network, with specially designed optical matrix switches in the third stage, is developed to provide HDTV- program distribution services as well as TV phone services. The overall insertion loss and crosstalk characteristics of the matrix switches, and the feasibility of the system is proved. The constructed 32-fine photonic switching system is now successfully operating. To extend the line capacity so over one hundred laser diode optical amplifier employment is investigated as well. Some 128-line switching networks including one optical amplifier stage are presented and requirements for optical amplifier gain and matrix switch insertion loss to implement the networks are clearly indicated. Those requirements are almost within reach of the current intensive research activities on the LiNbO3 matrix switches and laser diode amplifiers. Owing to the experiment and investigations described above, it is concluded that a practical 128 more line photonic switching system can be fabricated in the near future.
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