2-38
OPTICAL TIME-DOMAIN REFLECTOMETER (OTDR)
The portable optical time-domain reflectometer (OTDR) is used to check loss at each splice, at each
connector, and of the entire system. Loss measurements are figured by using the same methods you would
use for wire loss measurements. The OTDR injects a short, intense laser pulse into the fiber and monitors
reflections caused by breaks, inclusions, microcracks, and discontinuities. Discontinuities appear as a
spike on the OTDR display. The loss at the discontinuity point is directly related to the distance between
the major pulse triggered by the laser and the spike. The manufacturer’s manual provides you with
conversion factors to figure actual losses and locations of the discontinuities.
OSCILLOSCOPE
An oscilloscope is used with an OTDR to provide visual evidence of fiber faults, connector and
splice locations, and attenuation locations.
OPTICAL MULTIMETER
The optical multimeter measures light sources and light in cable and at the detector, fiber cable
transmission loss, and connector splice loss. For cable transmission measurements, transmission through a
short length of cable is compared with transmission through a known longer length.
OPTICAL OHMMETER
The optical ohmmeter measures the input versus the output of light in an optical fiber. It displays
attenuation losses based on a comparison of known and unknown cable signals. It can be used in
manufacturing, connecting, and installing cable. It is as simple to use as a digital voltmeter.
OPTICAL POWER METER
The optical power meter measures current by converting light power from plug-in units, such as light
emitting diodes, into electrical current. In some models, the readout is in power units, watts. In other
models, the readout is in absolute power levels and attenuation. Some units operate with a variety of
power sensors for conventional coaxial and waveguide systems and fiber-optic systems.
RADIOMETER/PHOTOMETER
The radiometer/photometer measures light power in watts from dc to unlimited ac response. It uses
plug-in sensor heads and, for low-light displays, it uses spectrometers and fiber-optic measurements.
AUTOMATIC TEST EQUIPMENT
Automatic Test Equipment (ATE) is test equipment designed to evaluate the operational
performance of a piece of equipment or printed circuit board (pcb). ATE assists you in troubleshooting a
fault to the defective component. Basically, ATEs are state-of-the-art, computer devices in which
software programs are specifically tailored to meet the requirements of the device being tested.
The AN/USM-465 Portable Service Processor (psp), shown in figure 2-32, is the Navy’s standard
ATE for testing digital pcb’s.
