Moog Components Group Prizm Fiber Optic USB 1.1 Link Manual
February 17, 2009
Page 8 of 9
2 Appendix A: Optical Considerations
2.1 Prizm Fiber Optic USB 1.1 Link Singlemode, Single Fiber Operation
The Prizm Fiber Optic USB 1.1 Link is configured for use with only singlemode fiber optic cable in
the umbilical and with fiber optic rotary joints (i.e. slip rings) at this time. Multimode cable cannot be
used.
Single fiber operation is advantageous to maximize the number of spare fibers in an umbilical or slip ring.
Single fiber operation is implemented by using two different optical wavelengths to carry the uplink and
downlink data on the same fiber. The two wavelengths are filtered and combined by either an integral or
external WDM to remove any interference between the uplink and downlink signals. The laser
transmitters are fabricated with a specific wavelength (i.e. 1310 or 1550 nm) and transmit at these
wavelengths. The optical receivers are responsive to a wide range of wavelengths (typically 1000 to 2000
nm). The filtering function of the WDM removes the local transmitter’s wavelength (the undesired
signal) from the remote transmitter’s wavelength (the desired signal). The local transmitter’s signal can
feed back into the local receiver by the reflection from a poorly terminated fiber optic connector and
cause link errors.
