Provided is an apparatus for testing the performance of an optical transceiver by referencing various performance clocks provided by an OTU2 signal connection transceiver and an STM-64OC-192 signal. Forming a notched RF pulse includes altering, according to the data, at least one of the amplitude and phase of one or more selected components, where each of the selected components has a bandwidth within the bandwidth of the notched RF burst. The rotatable ring is also utilized in connection with a bearing member to facilitate smooth and efficient rotation of the rotatable ring. When the number of inlet links in each input switch n1 is equal to the number of outlet links in each output switch n2, and n1=n2=n, a three-stage network is operated in strictly nonblocking manner in accordance with the invention if m\u22673*n\u22121. Alternatively, the sensor surface may be covered with a coating having properties that inhibit the growth of tissue.