Eyemask diagram

The transmitter and receiver output signals must conform to the eyemask defined in Fibre Channel FC-PI Rev. 12 for 1062.5 Mbps data rates. The fibre channel eyemask follows. A low-pass filter is recommended for the transmitter (between scope and O/E converter), to eliminate the relaxation oscillation of the laser during measurement. A fourth-order Bessel Thompson filter is recommended for this measurement with cutoff frequency equal to 0.75 times the bit rate.

The mask of the transmitter eye diagram is shown in Figure 1.

Note: x1 shall be half the value given for total jitter at the gamma T point. The test or analysis shall include the effects of a single-pole, high-pass frequency-weighting function that progressively attenuates jitter at 20 dB/decade below a frequency of bit rate/1 667. The value of x1 applies at a total jitter probability of 10-12. At this level of probability, direct visual comparison between the mask and actual signals is not a valid method for determining compliance with the jitter output requirements.