Patent ID: 6822786
Filing Date: 2004-11-23
Classification: G02B

Abstract:
A fiber optic communication system for transmitting an optical signal comprising:a. a transmission system configured to transmit the optical signal; b. a first length of optical fiber coupled to the transmission system for carrying the optical signal; c. an amplifier coupled to the first length of optical fiber for amplifying the optical signal thereby forming an amplified signal having a gain; d. an all fiber optical filter coupled to the amplifier for filtering the amplified signal and flattening the gain, thereby forming a filtered signal, the optical filter including: i. a fiber optic core having a first diameter, a filter length, a first index of refraction, a first end for receiving the amplified signal, and a second end for transmitting the filtered signal; ii. an inner cladding formed concentrically about the fiber optic core, the inner cladding having a second index of refraction and a first thickness, wherein the second index of refraction is less than the first index of refraction; and iii. an outer cladding formed concentrically about the inner cladding, the outer cladding having a third index of refraction, wherein the third index of refraction is greater than the second index of refraction and the third index of refraction is less than the first index of refraction, wherein the the optical fiber is stretched to form: the filter length separating non-stretched input and output lengths: the first diameter including a reduced diameter core along the filter length; and the first thickness including a reduced thickness inner cladding along the filter length: and further wherein the optical fiber is stretched until evanescent coupling is achieved between the fiber optic core and the outer cladding along the filter length to flatten the gain of the optical signal; e. a second length of optical fiber coupled to the optical filter for carrying the filtered signal; and f. a receiving system coupled to the second length of optical fiber to receive the filtered signal.