On Deciding on a fibre optic cable a few important question arise.
What type of Cable?
We need to detect a signal over a distance of 45km using a multimode fibre optic cable. The two types possible to use are Stepped index or Graded index? We have decided on using a graded index cable as it has a low modal dispersion and high bandwidth.
What wavelength of light are we using?
The two main wavelengths used to transmit are 850nm or 1300nm. A low lost window sits at 1300nm so this will yield the lowest attenuation.
Important criteria
We need the longest cable possible so has the least splices - 45km needed
The lowest possible attenuation - 0.5dB per km found
A bandwidth of at least 12MHz
A cable that matches this description has been found.
Power Budget
A power budget has been calculated showing a loss of about 28 dBm
