# Optical Communications Homework Questions

Optical communications questions

1.3- Two 1-km fibers are spliced together. Each fiber has a 5-db loss, and the splice adds 1db of loss. If the power entering is 2mW, then how much power is delivered to the end of this combined transmission line?

1.4- A receiver requires 10mW as input power. If all the systems losses add up to 50db, then how much power is required from the source?

1.9- A fiber telephone cable contains 144 fibers, each capable of carrying 672 voice messages. A conducting telephone cable contains 900 copper twisted pairs, and each pair can carry 24 messages. Compare the capacities of the fiber and conducing cables. How many of the conducting cables are required to equal the capacity of the fiber cable? Repeat the calculations if each fiber operates at the DS-4 signals rate?

1.31-A fiber system operates at the SONET OC-768 rate. Compute the number of digitized voice messages that could be transmitted simultaneously by using time division multiplexing. According to figures in table 1.6, the maximum number of voice messages in an actual OC-769 system is 516,096. Why is this less than the number you calculated.

1.33 Consider an optical beam at 1550nm. Compute the wavelength in um, mm, m, and km. Compute the frequency in Hz, kHz, MHz, GHz, and THz. Compute the energy in joules.