Fiber Optic Design Guide - Maite y Mario

Troubleshooting
Commercially available test equipment such as Blonder Tongue’s FOTK Fiber Optic Troubleshooting Kit are effective
tools for locating problems with the fiber optic cables. The FOTK can also be used to verify that the transmitter is
indeed putting out light. Other common problems include using a transmitter as a receiver and vice versa, lack of continuity
in the optical fiber, lack of power (or reversed power), or improper input levels. The transmitter is optimized to
accept a 1-Volt sync-to-white video input signal and two 1-Volt RMS audio signals. Larger inputs will introduce nonlinearities
or interfere with function. Note that the transmitters and receivers are designed to work with a 75 Ω video
system and a 600 Ω or 10 Ω audio system. If problems persist consult Blonder Tongue’s Systems Engineering
Department.
Problem Check Comments
Check Tx/mux power If there are less than than +12 Volts
connection and polarity. between pins J1-1 and J1-2,
No optical power higher current power supply is
out of Tx/mux. required (at least 550 mA).
If the voltage on pin J1-1 is negative
with respect to the voltage on pin
J1-2, reverse the power supply leads.
Check power at the Tx/mux. If there is power present at the
No optical power Tx/mux, verify the proper fiber is
at the Rx/demux. connected to Rx/demux. If the proper
fiber is connected, ensure integrity of
the fiber.
Check optical power For this link to work properly, the
Signal out of Rx/demux at Rx/demux. receiver requires a minimum input
is noisy. power of -30 dBm. Be sure to ground
the case of the transmitter and
receiver.
Verify signal input at Tx/mux. Must be 1-Volt sync-to-white.
Check Rx/demux power If there are less than +12 Volts
connection and polarity. between pins J1-1 and J1-2, a higher
No signal out of Rx/demux. current power supply is required
(at least 550 mA). If the voltage on
pin J1-1 is negative with respect to
the voltage on pin J1-2, reverse the
power supply leads.
Verify input signal at Tx/mux. Must be 1-Volt sync-to white or less.
Larger signal will cause distortion.
Verify fiber size. Fiber should be 62.5/125 µm for
Signal out of Rx/demux multimode models and 9/125 µm for
is distorted. SM Models. Larger core fibers may
overload receiver. Verify that
Rx/demux power is within
specifications.
Video signal amplitude Verify signal input at Tx/mux. Video signal must be 1-Volt
out of Rx/demux is too sync-to-white.
large or distorted. Verify Rx/demux video Add 75 Ω terminating resistor.
output is terminated into 75 Ω.
Verify signal input at Tx/mux. Audio signal must be 1-Volt RMS
Audio signal amplitude Verify that the output is terminated
out of Rx/demux is too into a 600 Ω or 10 Ω load. Add 600 Ω or 10 Ω terminating
large or distorted. Do not connect either output resistor.
to the ground.
No Audio Output Verify switch 3 is set to baseband Switch 3 turns audio carriers “on”
setting on Tx. and “off”.
*Note: 850 nm video systems generally are bandwidth limited at distances over 1.5 km. When this occurs, the Rx/demux output
will not be usable even when sufficient optical power is received.
LABORATORIES, INC.
The Standard of Quality in TV Signal Distribution
Section 2
46
One Jake Brown Road, P.O. Box 1000
Old Bridge, NJ 08857-1000 USA
(800) 523-6049 • (732) 679-4000 • FAX: (732) 679-4353
www.blondertongue.com