The complete definition of PCM is to transform the sampled quantized values of the analog signal into a code called pulse code modulation (PCM device).
In a fiber-optic communication system, a binary optical pulse "0" code and a "1" code are transmitted in an optical fiber, which is generated by switching a binary digital signal to a light source. The digital signal is generated by sampling, quantizing and encoding a continuously changing analog signal, called PCM (Pulse-code modulation), that is pulse code modulation. This electrical digital signal is called a digital baseband signal and is generated by a PCM terminal. Now digital transmission systems use a pulse-code modulation system. The PCM originally was not used to transmit computer data, but rather to have a trunk between switches not just transmitting a single telephone signal. The PCM has two standards (presentational forms), E1 and T1.
China adopts the European E1 standard. The rate of T1 is 1.544 Mbit/s, and the rate of E1 is 2.048 Mbit/s.
Pulse code modulation can provide users with a variety of services, from digital data line services from 2M to 155M, as well as voice, image transmission, distance learning and other services. It is especially suitable for users who require high data transmission rates and require higher bandwidth.