摘要:
An RF optical signal processing system that can provide various filter functions by way of tapped delay lines with fiber Bragg gratings, variable weight taps, positive and negative taps and a short coherent length optical source. Such an RF optical signal processing systems is advantageous over corresponding RF electronic systems and offer the increased bandwidth and lower power consumption making the RF optical signal processing system suitable for various application such as avionics and satellite communications.
摘要:
The present invention provides a computer controlled apparatus and method for producing high quality fiber optic Bragg gratings. According to the invention, the apparatus (10) preferably includes a laser (12) for generating an ultraviolet beam (18), a rotatable scrapper mirror (32) disposed downstream of the laser (12) for receiving the beam (18) and an optical fiber (48) disposed adjacent an edge (84) of the mirror (32) for receiving a high fringe frequency interferrogram (86) formed by the mirror (32). The mirror (32) is coupled to a rotation stage (14) for rotating the mirror (32) about a pre-selected pivot point (36) relative to the angle of incidence of the beam (18) to vary the Bragg wavelength at the fiber core.
摘要:
An electro-optic modulator and a method for its use, in which an optical carrier is effectively suppressed for transmission of a radio-frequency (rf) modulating signal over an optical communication link, to provide improved demodulator performance. A carrier component is recovered from the modulator, amplified, and reused, to minimize the effect of optical carrier losses. In one embodiment of the invention, a modulator (10) with complementary output ports (20 and 22) generates a carrier-suppressed output (FIG. 2B) containing rf sidebands from one port (20) and a strong carrier component (FIG. 2C) from the other output port (22). The carrier component is filtered in a residual sideband filter (14), amplified in an optical amplifying medium (12) and returned to the modulator (10) as its carrier input. In a second embodiment of the invention, a modulator (30) with a single output port produces rf sidebands and a suppressed carrier component (FIG. 4A), all of which are amplified in an optical amplifying medium (32) and coupled to an optical circulator (34), which, in cooperation with a narrowband filter (36), separates the rf sidebands from the amplified carrier component, the latter being returned to the modulator (30) as the carrier input. In both embodiments, a suppressed-carrier optical signal is obtained for transmission over a communication link, but carrier losses are minimized by recovery and recirculation of the carrier. In an alternate embodiment of the invention (FIG. 5), a second modulator (40) removes any residual rf components and avoids any unwanted cavity resonance.