STUDY SUMMARY - IPMU

SUMMARY REPORT
WIDE FIELD FIBER-FED OPTICAL
MULTI-OBJECT SPECTROMETER (WFMOS)
Figure 3.11-2: Fiber Throughput and the Contribution from Various Components
The bulk attenuation of low-OH silica fibers, typically specified as loss in dB/km, is highly
wavelength dependent in the 400–1,000–nm band. This bulk attenuation is well characterized
and is practically independent of vendor or core size.
To facilitate WFMOS installation and maintenance, fibers need to be sectioned and arranged
for interconnection, which in turn introduces insertion losses. To connect up 2,400 fibers in a
reasonable time, multi-fiber connectors are necessary. Fabrication of custom very-high-density
fiber connectors with 30 rows of 28 fibers (rectangular pattern with fiber pitch of 200 μm) are
planned to support WFMOS. To support 2,400 fibers, three such mating connector pairs will be
fabricated, and the extra fibers will be used as spares or for alignment monitoring. LNA has built
and tested a 5 × 5-fiber connector as part of preliminary risk-reduction activities. Test results indicate
that the custom connectors meet requirements and that they can be scaled to the desired
fiber counts. In the current baseline, there will be just one connector in each cable, and the
throughput budget assumes an achievable connector efficiency of 88%.
To minimize insertion loss degradation with repeated mate/de-mate cycles, we plan to use a
dynamic connector scheme, in which one connector (mounted on a 3-DOF stage) is actively
aligned to the other connector during installation. Tests on prototype indicate that positioning
accuracies of