Fiber Optic Communication

1.  Block Diagram of fiber optic communication, selection of optical
fiber types for short haul, long haul and
 high speed data links, optical power and dispersion budget
calculations of fiber optic communication link
 Repeaters,
 optical fiber amplifiers,
 optical fiber transmitter
 optical fiber receiver design considerations

2.  Draw block diagram of fiber optic
communication

3. Prepared by Mrs. Pallavi Mahagaonkar for TYB.Sc(Ele)

4.  When communication distance exceeds 10km, the long haul
communication is very effective.
 Basically it is point to point communication system with
very high data rates
Node P
Node Q
Users
Users

5.  Low Losses
Number of repeaters should be low to have very low loss
Repeater spacing is more as much as 40km
Due to which installation and maintenance cost is low

6.  For manufacturing a long fiber special care has to be taken during
fiber drawing
 Unbroken fiber length of 5 km
 This will reduce the number of splices to be used
 Due to which power loss will be minimum

7.  The cable used in long haul communication need to face or
withstand harsh environmental conditions so cable should be
structurally sound

9.  In long haul communication cable cannot be brought back to
the laboratory for repairs
 Hence it is expected that all the field components including
fiber cable must be field repairable

10.  It is the inherent property of the optical fiber to provide secure
and private transmission
 So care is to be taken to maintain the privacy and security

11.  Now that the losses for the link have been identified, the
power at the receiver, which is the power output of the link,
may be calculated simply as [EIRP] [LOSSES] [GR], where the
last quantity is the receiver antenna gain
 Note carefully that decibel addition must be used
 The major source of loss in any ground-satellite link is the
free-space spreading loss [FSL], the basic link-power budget
equation taking into account this loss only.
 However, the other losses also must be taken into account,
and these are simply added to [FSL]. The losses for clear-sky
conditions are

12.  [LOSSES] = [FSL] + [RFL] + [AML] + [AA] - [PL] equation for
the received power is then
 [PR] = [EIRP] x [GR] - [LOSSES]
where [PR] received power, dBW
[EIRP] --> equivalent isotropic radiated power, dBW [FSL]
free-space spreading loss, dB
[RFL] --> receiver feeder loss, dB
[AML] --> antenna misalignment loss, dB
[AA] --> atmospheric absorption loss, dB [PL] polarization
mismatch loss, dB