In the cable tv industry LCOs are receiving the optical signal from the MSO. MSO sends this optical signal from the transmitters .LCOs receiving this signal from the OFC or Optical Fiber Cable.This OFC have laid in the network.At the LCO end there is optical NODE installed.The output of this fiber cable goes into the input of NODE because NODE have optical input.Thus LCOs receive the signal from the MSOs.
Suppose one fiber is going from MSO to LCO 1. In this ofc path if a tree is fall down and results OFC break.Now there is no any communication between MSO and LCO 1.Now LCO will call to MSO splicers that he is not receiving the Power at his input point.Now splicers will splice the fiber.
This process takes the long downtime.So there is a need for redundancy circuit.So that LCO can provide his service continuously.
What Is Network Redundancy
Simply network redundancy means is to provide better up time by using the redundant device in the network. This is called the Network Redundancy.The device used to perform this task is known as Network Redundant Device.
There are three types of Network Redundancy
(1) By Using Single Fiber
This is the simplest way for the redundancy.We need to use two different core in single fiber line.Then we need to send same signal in both fiber cores.So that the receiving end whenever receiver did not get the signal from one fiber then it can be manually or automatically shifted to other core of fiber.
The drawback is that if fiber is broken in the field for any reason then both core or fiber will break and we can not have signal at the LCO end.
(2) By Using Double Fiber In parallel
In this method we need to use two different fibers.These fiber goes parallel to each other.For any reason one fiber(primary fiber) have broken.Then the other fiber(secondary fiber) can provide us signal.
The drawback in this method is that if a tree have fallen on both the fibers then both fiber will break.Because both fibers are parallel to each other.Thus this method will increase our downtime.
(3) By Using Double Fiber In Ring
In this method we need to use two fibers.The signal would be same in both fibers in any core.But the difference is that the route of both fiber would be different.The route can be in ring.So that if there is break in one fiber then the other fiber can provide the signal at the LCO end.
There are very less number of chances that both fiber will break simultaneously.
What are Splitter Dividers Combiners
What Is Fiber Switch
Whenever the link gets down at lco side then lco needs to manually change the patch cord of fiber to shift the signal from different path or different fiber.In this process lco needs to be active the receiving end because as the link gets down he needs to switch the fiber patch cord of NODE as soon as possible to provide good service to their subscribers.
Now this is not possible for lco to be active the receiving end 24 hours.To opt out this situation switches were developed.These switches are called the fiber switches.
Fiber switch is a active switch.This switch is installed at the receiving end of the LCO before the receiving device this receiving device can be NODE.
Now when the link gets down from MSO to LCO path then this fiber switch automatically shifted to redundant patch of fiber.This fiber switch have two input from different path of fiber.
Installation Of Fiber Switch
installation of fiber switch is very easy.We need to mount this fiber switch before the receiving device of LCO.Fiber switch have two input then we need to connect it with our two inputs of fiber from different cores or different path.
We need to manually set the minimum threshold value for the switch.So that when the switch receive the signal level below this threshold level then it automatically shifted to secondary fiber.
Different types of fiber switch is available in the market we need to purchase accordingly wavelength like 1310 nm or 1550 nm.Because same switch can not be used for both wavelength.
Working Of Fiber Switch
For example we can have two fibers at the lco end known as primary fiber and secondary fiber.So when the primary fiber link gets down.This fiber switch automatically switch the output from primary fiber to secondary fiber.So when the primary link gets up then again this switch automatically shift output from secondary fiber to primary fiber.
The downtime for the redundancy is very low approximately 10 mili seconds.
In case if the fiber switch power supply is down then it will send output from primary fiber only.It will not then shift from primary fiber to secondary fiber.
Fiber switch does not change the value of signal.It sends the signal as it is.The only difference is that it can loss in signal level within 1 dBm to 1.3 dBm.So network engineer should consider this loss of fiber switch and then he should maintain the network.
This is all about what is fiber switch and Network Redundancy.
Know More About What Is OFC Or Optical Fiber Cable
