The optical power meter loses power as soon as red light is used
When combined with a light source, the instrument is called an Optical Loss Test Set, or OLTS, and is typically used to measure optical power and end-to-end optical loss. A typical OPM is linear from about 0 dBm (1 milli Watt) to about -50 dBm (10 nano Watt), although the display range may be larger.
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