616 17 16 15 R-OSNR (dB) 14 13 12 11 10 9 8 -30 -20 Optical System Performance Measurements OSA resolution bandwidth: 0.1 nm Q = 3.57 dB 2 2 1 1 1 5 0 -10 0 10 Frequency offset (GHz) 20 30 Figure 5.8.12 Measured R-OSNR as a function of the transmitter frequency offset. example of the measured R-OSNR as a function of the transmitter frequency off- set for different numbers of circulations of the optical recirculating loop as indi- cated beside the corresponding curve. For small numbers of loop circulations, the WSS optical bandwidth extends to approximately Æ20 GHz. When the optical