$($a$)$ Define each of the following as used in data communication:

$($i$)$ multiplexing;

$($ii$)$ channel;

$($iii$)$ guard bands.

$(3$ marks$)$

$($b$)$ With the aid of a labelled diagram, describe the principle of operation of wavelength division multiplexing $($WDM$).$

$(6$ marks$)$

$($c$)$ Four channels are multiplexed using time division multiplexing. Each channel sends $100bps.$ One bit is multiplexed per channel. Determine the:

$($i$)$ size of the frame, in bits;

$($ii$)$ frame rate;

$($iii$)$ duration of a frame;

$($iv$)$ bit rate of the link.

$(8$ marks$)$

$($d$)$ Table $1$ shows part of analog frequency division multiplexing hierarchy. Complete the table.

$(3$ marks$)$

Table $1$

$\backslash$table$[[$Type of Hierarchy,$\backslash$table$[[$No$.$ of Voice chan$-],[$nels$]]],[$Group$,],[$Supergroup$,],[$Jumbo group,$3600],[$Master group,$]]$