Differences

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--- fiber_run [2024/04/29 14:29] – holtz
+++ fiber_run [2024/09/11 21:30] (current) – holtz
@@ Line 1: / Line 1: @@
+====== Fiber ======
+===== Fiber cladding and termination =====
+We inherited fiber from the Australia SONG project. This was about 500 meters of octagonal (50/70/95) fiber. We signed a contract with FiberTech Optica (FTO) in Canada to construct 2 separate 83m cables (for redundancy), each with 3 fibers in it (for science fiber, cal fiber, and extra fiber), with a ferrule on one end and a FC connector on the other, and sent them the fiber in July 2024.
+However, FTO has had issues with that fiber:
+- for a short (2m) segment, they measured 25% lower throughput than the same length of circular fiber
+- for an 83m segment, they measured 80% throughput at 632nm (not so far from the 86% that we were anticipating)
+- most troubling, they say the fiber came off the spool very twisted and stressed, so that it coils itself back up, and is very difficult to work with. Injecting a slow beam, they estimate 40% loss in an output f/6 beam, and thus, likely worse for an input f/6 beam (which they will test).  Since they used
+the same spool for the Australia SONG node a few years ago, they looked up the notes for that, and found that the technician who handled that fiber described it as "devil fiber", so it perhaps had the same issues back then. They did not recall doing FRD testing at the time. If FRD was not tested, this perhaps might have implications for performance at the Australia node.
+As of September 2024, we are considering how to proceed.
+===== Fiber conduit =====
 ==== Fiber run measurements, April 2024: ====
@@ Line 27: / Line 47: @@
 MARVELS room wall length ~6 meters, so need additional depending on where spectrograph is located
-==== Some images of fiber run ====
+==== Images of fiber run ====
 ==  Small junction box into APOGEE raceway ==
-{{::fiber:fiber1.jpg?direct&300 |}}
+{{::fiber:fiber1.jpg?direct&300 |Small junction box into APOGEE raceway}}
@@ Line 37: / Line 58: @@
 == New conduit around SDSS ==
+{{::fiber:fiber2.jpg?direct&300 |New conduit around SDSS}}
-{{::fiber:fiber2.jpg?direct&300 |}}
 {{::fiber:fiber3.jpg?direct&300 |}}
@@ Line 48: / Line 68: @@
 == Raw fiber from Polymicro ==
+{{::fiber:rawfiber1.jpg?direct&300 |Raw fiber from Polymicro}}
-{{::fiber:rawfiber1.jpg?direct&300 |}}
+{{::fiber:rawfiber2.jpg?direct&300 |Raw fiber from Polymicro}}
-{{::fiber:rawfiber2.jpg?direct&300 |}}
-{{::fiber:rawfiber3.jpg?direct&300 |}}
+{{::fiber:rawfiber3.jpg?direct&300 |Raw fiber from Polymicro}}