Question $1(6$marks$)$

a$)$ Describe the main functions of OADM $($Optical Add Drop Multiplexer$)$ and mention two of its most

used applications? $(3$ Marks$)$

b$)$ CDMA is an example of multiple access and is widely used in some mobile telephony techniques.

Briefly explain what is meant by multiple access and what distinguishes multiple access from

multiplexing? $(3$ Marks$)$