Optical Loss Test Set, a stable light source at one end and a calibrated power meter at the other, often packaged as a matched pair that measures two wavelengths in both directions. After setting a reference with test jumpers, the meter reads the link's insertion loss directly. This is the basic certification test, usually called Tier 1, and it is the measurement that best matches what transceivers will see.
Tier 1 is OLTS only, two wavelengths each way, and the report goes to the owner before we pull the lift.
Also heard as
- light source and power meter
- LSPM
- loss test set
Do not mix it up with
- OTDR: An OTDR maps events from one end; an OLTS measures total loss from end to end.
Related terms
Insertion loss
The optical power lost when a component or a whole link is placed in the light path, measured in dB.
One-jumper reference
A loss-test reference set with a single launch jumper between source and meter, so both link end connectors are counted.
Loss budget
The calculated total loss a fiber link should have, built from fiber length, connectors and splices.
dBm
Optical power in decibels relative to one milliwatt, the unit of power meters and transceiver specs.
OTDR
Optical Time Domain Reflectometer: a tester that maps a fiber's loss and events by timing light reflected back along it.