Switch parameters

For all applications of optical fibers, switching plays an important role. In optical communication or data storage, the signals coming from one transceiver have to be directed to one of a number of receivers. In optical spectroscopy the information from different probes must be given to the spectrometer head in a time multiplexed way. Finally a switchable high power beam delivery system can switch the light tool between a number of working stations and thus increase system flexibility and cost. There are several key parameters for fiber optic switches that are common for all the applications mentioned above.

1 x N

P

1 out

Switch

P

2 out

P

in

P

i out

P

r

P

N out Insertion loss [ dB ] - L
i = 10
* log (P
in /P
i out ) Crosstalk [ dB ] - C
j = 10
* log (P
j out /P
i out ); for signals switched to output channel i Back reflection [ dB ] - R = 10
* log (P
r /P
in ) Switching time

Ï„

- time difference of the 10% - 90% output power transition in the switched channel. The typical parameters for different applications are given in the following table

Communication Optical Measurement Storage systems

Insertion loss < 2dB < 1 dB < 1dB Crosstalk – 50dB appr. -30 dB typ. -30 dB Back reflection –60 dB non critical non critical <5 ms < 1 ms typ. < 100 ms