Draw the diagram of two fiber UPSR and explain how it is useful in stand by mode of continuous fiber optic communication

 

Block Diagram of Two fiber UPSR









The full form of UPSR is Two Fiber Unidirectional Path Switched Ring (UPSR).
Normally the working of traffic travels clockwise around the ring on primary path.

Connection from Node 1 to Node 3 links 1 & 2.
Traffic clockwise path is the protection path, if the link or Node fails, protection path (Link 5 to 8) is indicated by dashed lines.

To achieve protection, signals from a transmitting Node is a dual fed into both primary and protection fiber.

In case of failure of fiber optic communication, how does four fiber BLSR help. Explain with neat diagram

 

The full form of BLSR is Bidirectional Line Switched Ring.
Two primary fiber loops (1p to 8p) are used for normal bidirectional communication.
And other two secondary fiber loops are stand by links for protection purposes (1s to 8s).

Lets consider, the connection between Node 1 and Node 3 then traffic from Node 1 to Node 3 flow in clockwise direction links 1p & 2p.
In return path, traffic flow counter clockwise from Node 3 to Node 1 along links 7p & 8p.
If a transmitter or receiver circuit card fails, then the affected Node detects a loss of signal condition.
And switches both primary fiber connecting Nodes to secondary protection pair.

So in that condition four fiber bidirectional line switched ring is very useful and helpful.