Extended Sensitivity Meters
A class of laboratory power meters has an extended sensitivity, of the order of -110 dBm. This is achieved by using a very small detector and lens combination, and also a mechanical light chopper at typically 270 Hz, so the meter actually measures AC light. This eliminates unavoidable dc electrical drift effects. If the light chopping is synchronized with an appropriate synchronous (or "lock-in") amplifier, further sensitivity gains are achieved. In practice, such instruments usually achieve lower absolute accuracy due to the small detector diode, and for the same reason, may only be accurate when coupled with singlemode fiber. Occasionally such an instrument may have a cooled detector, though with the modern abandonment of Germanium sensors, and the introduction of InGaAs sensors, this is now increasingly uncommon.
Read more about this topic: Optical Power Meter
Famous quotes containing the words extended, sensitivity and/or meters:
“Crotchless trouser allows wearer to show private parts in public. Neoprene-coated nylon pack cloth is stain resistant, water repellent and tickles thighs when walking. Tan-olive shade goes with most fetishes. Adjustable straps attach to belt for good fit and easy up-down. Pant is suitable for fast exposures as well as extended engagements. One size fits all.”
—Alfred Gingold, U.S. humorist. Items From Our Catalogue, “Flasher’s Pants,” Avon Books (1982)
“...some small boys came out of the city and jeered at him, saying, “Go away, baldhead! Go away, baldhead!””
—Bible: Hebrew, 2 Kings 2:23.
Elisha--proving that baldness has been a source of sensitivity for centuries, Elisha cursed them and they died.
“In our Mechanics’ Fair, there must be not only bridges, ploughs, carpenter’s planes, and baking troughs, but also some few finer instruments,—rain-gauges, thermometers, and telescopes; and in society, besides farmers, sailors, and weavers, there must be a few persons of purer fire kept specially as gauges and meters of character; persons of a fine, detecting instinct, who note the smallest accumulations of wit and feeling in the bystander.”
—Ralph Waldo Emerson (1803–1882)