>
2009: round trip phase test of alfa fibers @5Ghz
Alfa fiber notes.
05apr08- Fiber Span AC231, Fiber Optic Xmtr/Rcvr
measurements by bsisk\
Phase drift alfa fibers:
Dana did a round trip to platform test
using a pair of alfa fibers in 2009. He transmitted a 5 Ghz tone from
below, put a barrel to connect the two fibers upstairs, and then
compared the output phase with the input phase downstairs. The test
started at 13:00 on a partly cloudy day and went for 8000 seconds. The
telescope was stationary during the measurement.
The plot shows
the phase
drift over the 8000 seconds (.png):
Alfa fiber optics
notes.
- Fiber
Tx Notes (from fiber span rep:)
- For a clean(i.e., very linear) signal, we recommend staying 10
dB or more below the 1dB compression point, putting the "peak linear
power" at +5 dBm.
- The damage threshold for these devices is an input power of +20
dBm. Please do not exceed this maximum, even for very short durations.
- Amp bias:
- The RF and IF amps are not
properly biased (according to the data sheets). Proper biasing caused
oscillations in the board. Ganesh thinks that the actual biasing may
decrease the gain of the combined amps by up to 3db.
- Input Levels for compression:
- -27Dbm at input to RF
amp will cause 1 db compression at mixer output (assuming 20 db gain
for misbiased RF amp).
- Input Levels for damage to fiber
Optic transmitter.
- A peak level of +20dBm
will damage the fiberOpticTx.
- With +45 db gain
- a -25 dBm signal would cause problems if No compresssion.
- a -27 dBm signal will be 1db compresses at the mixer output.
