Amplifiers – Parametric amplifiers – Semiconductor type
Patent
1989-08-08
1990-10-16
Moskowitz, Nelson
Amplifiers
Parametric amplifiers
Semiconductor type
350 9615, G02B 626, H01S 3094
Patent
active
049638327
ABSTRACT:
This invention is directed toward reducing substantially the loss incurred when two optical fibers of different mode diameters are coupled together. In this invention, the coupling of one fiber to that of another where the fibers are of different mode diameters is not with a tapered fusion, core-to-core splice, but with an evanescent field fiber coupler. Briefly, to achieve amplification of a weak optical signal, an amplifying fiber is inserted into the system at one or a plurality of locations. More specifically, at a desired location, the transmission fiber is severed to provide two sections and the severed sections are transversely coupled to the amplifying fiber. The weak signal from the first section of the transmission fiber is coupled into the amplifying fiber via a first evanescent field type of fiber coupler; and the amplified signal is coupled from the amplifying fiber to the second section of the transmission fiber via a second evanescent field type of fiber coupler. The first evanescent field type of fiber coupler is designed to couple substantially all of the signal energy from the first section of the transmission fiber to the amplifying fiber and to couple substantially none of the laser diode pump signal or energy from the amplifying fiber to the transmission fiber. The second evanescent field type of fiber coupler is designed to couple substantially all of the signal energy in the amplifying fiber to the transmitting fiber and substantially no laser diode pump energy is transferred from the amplifying fiber to the transmission fiber. Either or both cut ends of the transmission fiber can be coupled to monitor devices to detect and determine the value of the signal being coupled into and/or out of the amplifying fiber to control, for example, the gain of the amplifying fiber.
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Desurvire Emmanuel
Giles Randy C.
Whalen Matthew S.
AT&T Bell Laboratories
Moskowitz Nelson
Weiss Eli
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