This paper presents the design and performance features of a successfully developed optical intraoffice transmission system operating at 100-400 Mbits/s. The keys to the commercial realization of this simple, highly reliable, and low-cost system are the employment of the 1.3 μm LED and graded-index multimode fiber. Additionally important, the system makes use of coded mark inversion (CMI) coding to ensure bit sequence independence (BSI) and good error-monitoring capability. Experimental results have clarified the optimum bandwidth of the low-pass filter at the receiver end and the commercially attainable transmission distance. Furthermore, an available system gain of 15.4 dB is demonstrated through 400 Mbit/s transmission experiments. This value enables transmission over distances in excess of 4 km through multimode fiber (900 MHz\cdotpkm, 0.8 dB/km).

In equalization design of submarine coaxial cable system, the cable attenuation deviation due to pressure in deep sea bottom has significant weight. This paper treats the submarine coaxial cable characteristics pressure dependency. By using an artificial ocean test facility, 1.7 inch submarine coaxial cable attenuation, phase, capacitance and insulator core diameter were studied and their pressure coefficients under a pressure of 0 to 500kgw/cm^{2}at temperatures of 5, 10 and 20°C were obtained. In this study, pressure dependence of polyethylene dielectric constant and dissipation loss were quantitatively analyzed. The attenuation pressure coefficient varies with frequency. For example, cable attenuation in the sea at a depth of 5000 meters is higher than that on the land by 1.09 percent at 10 MHz and by 1.54 percent at 60 MHz at a temperature of 10°C.