MRV Communications EM316E3 - Manual (Page 9)

Fiber Driver
EM316E3 & EM316E3SF
P/N: 1226006-001, REV_L PAGE 9
Theory of Operation
Block diagram of the Modem/Converter is shown below (fig. 1)
Fig. 1 Block Diagram of EM316DS3
E3 Line Receiver to fiber optic Transmitter :
The receiver Line Interface Unit (LIU) receives the E3 signal and performs clock recovery and
data detection. The data goes through B3ZS Decoding Block to extract NRZ data. It then goes to
an encoding block and is ready to be transmitted by the Fiber Optic Transmitter Interface.
Fiber optic Receiver to E3 Transmitter :
The fiber optic Receiver Interface directs the received signal to a decoder in order to extract the
NRZ data. The NRZ data is going through B3ZS encoder and then to the E3 Transmitter.
Loop Back :
This feature isolates the optic side from the E3 side, and enables each side to loop back on its own
media line as shown below:
Switch LPBK/NORM is set to ON
When switch LPBK/NORMAL is turned ON, the card is configured as follows:
Optic input to the receiver is looped back into optic transmitter, thus enabling remote site to
perform loop back on fiber optics. Note that this loop back includes the encoder and decoder
blocks of the fiber optic. E3 receiver input is looped back into E3 transmitter, thus enabling full
loop back on E3 line side. The route of the loop back includes the logic of decoder and encoder
blocks of the E3.
Loopback
On E3
side
Loopback
On Fiber side
Fig. 2
Coax to
near DTE Fiber to far
EM316E3
E3
Receiver B3ZS
Decoder
Encoder
FI
Transmitter
E3
Transmitter B3ZS
Encoder Decoder FI Receiver
Fig. 1