Subscribe by Email

Thursday, June 27, 2013

What is the difference between a passive star and an active repeater in fiber optic network?

There are two important components of a fiber optic network namely passive star coupler and active repeaters. 

Passive Star in Fiber Optic Network
- Passive star couplers are single mode fiber optic couplers with reflective properties.  
- These couplers are used for optical local area networking at very high speeds. 
- These couplers are made from very simple components such as mirrors and 3 db couplers. 
- Besides this, these star couplers save a lot of optical fiber when compared to its trans-missive counterpart. 
- They are free of any multi-paths so as to avoid any interference. 
- A fiber optic network may consist of any number of passive star couplers and each of them is capable of connecting a number of users. 
- The input and output from every passive star coupler is given to the output and input of an active coupler. 
- The round trip transmission tile is stored by the active star coupler. 
- When it receives a signal from a passive star coupler, it stops the output to that coupler for the duration of the signal.
- It also inhibits the incoming data from all the other passive star couplers for the round trip transmission delay plus signal duration. 
- The purpose of a star coupler is to take one input signal and then splitting it in to a number of output signals. 
- In telecommunications industry and fiber optics communication, this coupler is used in network applications being a passive optical device. 
- If an input signal is introduced to one of the input ports, it is distributed to all of the output ports of the coupler. 
- As per the construction of the passive star coupler, the number of ports it will have is given by the power of 2. 
- For example, in a two port coupler or in a directional coupler or splitter, there are 2 input ports and 2 output ports.
- In a four port coupler, there are 4 i/p ports and 4 o/p ports and so on. 
- The digital equipment corporation also sold a device by the name of star coupler which was used for interconnecting the links and computers through coaxial cable instead of using optical fibers. 

Active Repeater in Fiber Optic Network 
- Active repeater is an important telecommunications device used for re transmitting the signal it receives to a higher level and with higher basically to the other side of an obstacle so that long distances can be covered. 
- Repeater is an electro-mechanical device that helps in regenerating the telegraphy signals. 
- It may be defined as an analog device for amplifying the input signal, reshaping it, re-timing it for re-transmission. 
- A re-generator is a repeater that can perform the re-timing operation. 
Repeaters just tend to amplify the physical signal without interpreting the data transmitted by the signal. 
- The 1st layer i.e., the physical layer is where the repeaters operate. 
Repeaters are employed for boosting the signals in optical fiber lines as well as in twisted pair and coaxial cables. 
- When a signal travels through a channel, it gets attenuated with the distance and time because of the energy loss (dielectric losses, conductor resistance etc.). 
- When light travels in optical fibers, it scattered and absorbed and hence is attenuated. 
- Therefore, in long fiber lines, repeaters are installed at proper intervals for regenerating and strengthening the signal. 
Repeater in optical communication performs the following functions:
Ø  Takes the input signal
Ø  Converts it in to electrical signal
Ø  Regenerates it.
Ø  Converts it in to optical signal
Ø  Re-transmits it

- These repeaters are usually employed in submarine as well as transcontinental communication cables as the loss is unacceptable in these cases.  

No comments:

Facebook activity