19
CHAPTER 4: Operation
4.3.2 R
EMOTE
L
OOPBACK
T
EST
This test can be done only with a pair of Converters, one on either side of
the single-mode line. Move the TEST switch on the front panel of the local
Converter to the REMOTE (right-hand) position. The local Converter will
light its ON LOCAL and ON REMOTE LEDs; its Remote Loop Generator
will contact the remote Converter’s Remote Loop Detector, causing the
remote unit to light its ON REMOTE LED and to stop accepting data from its
Multimode to Single Mode IN 850NM or IN 1300NM connector. (The remote
Converter’s TEST switch should remain in the NORMAL [center] position.)
Begin sending test data from the BERT to the local Converter. The data will
travel along this path (minimally illustrated in Figure 4-4 below):
• Into the local Converter’s Multimode to Single Mode IN 850NM or IN
1300NM connector, through its MUX MM/SM, and out of its Multimode
to Single Mode OUT 1300NM connector;
• Across the line, into the remote Converter’s Single Mode to Multimode
IN 1300NM connector, through its MUX MM/SM, and out of its
Multimode to Single Mode OUT 1300NM connector;
• Back across the line, into the local Converter’s Single Mode to Multimode
IN 1300NM connector, through its MUX SM/MM, and out of its Single
Mode to Multimode OUT 850NM or OUT 1300NM connector; and
• Back into the BERT.
As in the local test, the tester reports discrepancies between the sent and the
received data streams. When the test is done, move the local Converter’s
TEST switch back to the NORMAL (center) position. It will turn off its ON
LOCAL and ON REMOTE LEDs and instruct the remote unit to resume
normal operation and to turn off its ON REMOTE LED.
FIBER
OPTIC
EQUIPMENT
FMC-101
FMC-101
PTT
LINES
FIBER
OPTIC
EQUIPMENT
Figure 4-4. Remote loopback.
BERT
MULTIMODE
EQUIPMENT
FOC
FOC
