# Optical fibers problem

1. Dec 16, 2014

### Saeed.z2010

1. The problem statement, all variables and given/known data

Below is the original question and I just want to check out my answer of part one only.

A single mode optical fiber link is required to link two major cities that are 1500 Km apart. The link must be capable of transmitting a minimum (NRZ) data rate of 10Gbps. The properties of the optical fiber to be used in the link are as following :
Core diameter: 8.0 micrometer
Core / Cladding refractive indices : 1.45 / 1.445
Operating Wavelength :1.55 micrometer
Fiber attenuation: 0.22 dB/Km
Splice Loss: 0.04 dB per splice
Longest continuous cable length available: 1.0 Km
Type of fiber: Single mode / Step Index
Combined Material and Waveguide Dispersion Parameters: 6 ps/(nm.Km)

Repeaters are required in the construction of the link. Assume that all repeaters are identical and that each repeater is cable of perfectly regenerating the digital bit stream (provided the incident optical power is not less than the threshold power of the repeater's photodetector and that pulse spread does not exceed a preset value).The following are the properties of each repeater:
Detector Threshold Power: 1.60 micro-Watt
Source Output Power: 3.4 mW
Source Wavelength: 1.55 micrometer
Source Spectral Width: 0.08 nm
Source Type: High Quality Laser Diode

Assume that the optical source used at the input end of the link has the same characteristics as the source used in the repeater and that the detector at the output end of the link has the same characteristics as the detector used in each repeater. Assume also that there is no optical power loss at the input or the output sides of the repeater.
1- The total number of repeaters used in the link must be minimal.
2-allow for a total of 8dB power loss between repeaters due to unforeseen causes of loss and also for the possibility of future splices.

Calculate the following:
1- The distance that separates the individual repeaters.
2- The total number of required repeaters.
3- The total number of splices needed to construct the entire link.

2. Relevant equations

3. The attempt at a solution
I used only the equations stated above and found out the value of L as 145.83 Km.

hence, the distance between two repeaters should be 145.83 Km.

any reply would be appreciated. Thank you.

2. Dec 21, 2014