| 摘要 |
<p>A tunable etalon filter is formed by placing mirrors (12,24) on either side of a spacer (22) of a material which has a relatively large rate of change of refractive index with temperature, and coupling the filter to a temperature control means to control the temperature and, therefore, the index of reaction of the spacer. More specifically, the spacer can be a silicon wafer, or of zinc side or zinc selenide or the like. The mirrors (12,24) can be formed of quarter wavelength layer pairs of dielectric coatings of high and low refractive index material. The temperature control means can be a thermoelectric coder coupled to a heat sink to control the temperature of the spacer by either heating or cooling. The filter is coarse tuned to a desired channel by adjusting its angle relative to the angle of the received optical signal. It is then locked to the transmitter signal by adjusting the temperature of the spacer. The advantages of this filter are: large tunability by angle tuning; control of the transmission wavelength by means of temperature; large free-spectral-range; narrow passband; low insertion loss; and high reliability. <IMAGE> <IMAGE></p> |
