OPTCAL SWITCHES Requirments basic design ant
techology. Until the late 70s the
switching and control of the data stream
was made on electrical signais not on optical. Since then, theoptical switches,is been used in optical fibers networke. Op switches advantages ,save to transforms of signals to ei signals,faster,low snr,ersir control and feasibility. We need switches for ,provisonig,protection
switching ,packet switching,external modulation. Provisioning in this appliction,the switches are used inside wavelength cross connects to reconfigure them to support new light paths. For this appliction the switches are replacement for manual fiber patch panels,but with added software for end to end management. this appliction,the switches with milliscond switching time is acceptable. The challenge here is largs switch size. Here protection switching ,the sweitches are used to switch the traffic stream from primary fiber onto anoter fiber in case the primary fiber fails. The switching time required is few milliscond. The packet switching use for hign speed optical packet sweitched networks. The switching time must be much smaller then the packet duration. The switching time required for efficient operation is in the order of few nanoseconds. Use external modulation to turn on and off the data in front of the laser source. In this case ,the switching time must be a small fracton of the bit duration. For modulator of 10 gb/s with a bit duration of 100 ps ,must have s t of 10 ps. Parameters switches , number of ports,switching time,extinction ratio,crosstalk ,polarizaton dependent loss,reliabiability. In large optical switches building considerations , nmber of switch element required,loss uniformity,number of crossovers, blocing characteristics. Ther are mems switches - Micro Electro Mechanical Systems. In eo switches ,miniature movable mirros fabricated in silicon,large scale array. Switch bubble based waveguide ,light channels crossed by index matching fluid trenches. In normal condition,light propagate in one waveguide though the trench,if the fluid under the trench in a crossover is being heated ,an air bubble appears ant the light reflects to another waveguide Liquid criystal switches by applying a voltage to suittably disigned liquid cryestal cell we can cause to control the polarization of the light. This combind with passive polarization beam splitter and combiners. The electro-optic switches by applying xoltage to suitable materiel like the lithium niobate (liNbO3) we canchange the refilective region in the coupling region. The are semicondouctor optical amplifier switches can be used as an on-off switch by varying the bias voltage. Under the threshold voltage- no inversion of population above the threshold voltage ampilfication. Thank you.