摘要:
An optical fiber amplifier is pumped by a pair of pump lasers which have at least partially overlapping resonators. In one embodiment, the fiber gain section of the amplifier is located external to the resonators. In another embodiment, the coupler, which couples the pump lasers to the gain section, is located at least partially within said resonators. In a preferred embodiment the resonators are provided with polarization selection properties, and the outputs of the pump lasers are coherent.
摘要:
An optical fiber amplifier is pumped by a fiber pump laser which has a pair of separate active media within a common resonator. The fiber gain section of the amplifier is also located within the resonator.
摘要:
In an optical fiber light source a section of multimode fiber is interposed between an energizing laser (e.g,, a diode laser) and a single mode fiber active medium. In a preferred embodiment the single mode fiber active medium is surrounded by a multimode cladding coupled to the multimode fiber. The source may serve as a pump laser for a fiber amplifier or as an amplified spontaneous emission source. Arrangements for coupling several energizing lasers to the active medium are also described.
摘要:
An upgrade method in which Raman amplification is added to an existing transmission system to provide an increase in power budget and permit a substantial increase in transmission capacity either by time division multiplexing (TDM), wavelength division multiplexing (WDM), or a combination thereof. The power budget improvement permits higher transmission capacity by increasing either a single channel data rate and/or the number of wavelength division multiplexed data channels that can be accommodated by existing fiber links.
摘要:
A low noise optical fiber Raman amplifier (FRA) comprises an upstream and a downstream length of silica-based amplifier fiber, of combined length >200 m, typically >1 km, with an optical isolator disposed between the upstream and downstream lengths of amplifier fiber such that passage of backscattered signal radiation from the latter to the former is substantially blocked. In preferred embodiments counter-propagating pump radiation is coupled into the downstream length of amplifier fiber, and wavelength-selective means are provided for shunting the pump radiation around the optical isolator. The described FRA is advantageously incorporated into optical fiber communication systems. Exemplarily it can serve as power amplifier, as pre-amplifier, or as in-line amplifier. For instance, it can be used to replace conventional opto-electronic repeaters in existing 1.3 .mu.m fiber communication systems, or it can be used as power amplifier in a multi-subscriber optical fiber CATV system. In a still further exemplary embodiment, the FRA is used as a distributed pre-amplifier in a remotely pumped fiber communication system.
摘要:
A high speed optical communication system (≧10 Gbit/s) is compensated for temperature variation by providing it with one or more automatic dispersion compensation modules. Each module has an adjustable dispersion element, a data integrity monitor and a feedback network whereby the monitor adjusts the dispersion element to compensate for temperature variation. In a preferred embodiment the dispersion compensating modules comprise chirped fiber Bragg gratings in which the chirp is induced in the grating by passing a current along distributed thin film heaters deposited along the length of the fiber. The magnitude of the applied current determines the dispersion of the grating. A data integrity monitor is configured to sense the integrity of transmitted data and to provide electrical feedback for controlling the current applied to the grating.
摘要:
Magnets are used to control the amount of coupling loss between fibers. The fiber ends are attached to magnets and by controllably magnetizing the magnets, the fibers can be pulled apart or brought closer together to vary the amount of coupling loss. Preferably at least one of the magnets is latchable. The advantage of the latchable version is that a predetermined amount of loss can be latchably set by magnetizing the magnets to a particular level and afterwards no additional power is required to maintain the amount of attenuation. This is advantageous compared to other approaches in which power is required continuously to maintain a particular loss level.
摘要:
An optical fiber communication system according to the invention comprises an optical fiber filter that can be manufactured at low cost and that can be conveniently incorporated into the system, substantially like a conventional fiber jumper. The filter comprises a length L of axially uniform optical fiber selected to have substantially no loss (e.g., 20 dB) at a wavelength .lambda..sub.2. The length L will typically be less than 100 m. In one embodiment the optical fiber is a single mode optical fiber at .lambda..sub.1 (e.g., 1.3 .mu.m) that does not have a guided mode at .lambda..sub.2 (e.g., 1.55 .mu.m). In another embodiment the fiber contains a dopant that does substantially not absorb radiation of wavelength .lambda..sub.1, but substantially absorbs at .lambda..sub.2. In the second embodiment, .lambda..sub.1 can be greater than .lambda..sub.2. Fiber filters according to the invention can be advantageously used in a variety of communication systems, and exemplary systems are disclosed.
摘要:
A large optical preform 303 is made by a modified chemical vapor deposition (MCVD) process by depositing successive layers of core and cladding materials onto the inside surface of a rotating glass tube 33 having a hydroxyl ion (OH.sup.-) level that is less than 0.5 parts per million (ppm) by weight. The tube is then collapsed inwardly to form a core rod 301 in which the deposited core material 31 has a diameter that is greater than about 5 millimeters and the deposited cladding material 32 has an outside diameter that is less than about 15 millimeters. A machine-vision system 140, 150, 160 monitors and controls the diameter of the glass tube by regulating the pressure within the tube. Moreover, the machine-vision system monitors and controls the straightness of the tube by varying its rotational speed according to angular position. After the core rod 301 is formed, it is plasma etched to remove contaminants, and then overclad with two glass jackets 34, 35 having a hydroxyl ion (OH.sup.-) level that is less than 1.0 ppm by weight to create a large preform 303 from which about 400 kilometers of singlemode optical fiber can be drawn per meter of length.
摘要:
In one embodiment, an optical transmitter, which has a modulator disposed between an pair of optical amplifiers, exhibits reduced carrier-to-noise ratio and relatively high powers. In another embodiment, an optical amplifier is disposed between the laser carrier source and the modulator, but the post-modulator amplifier is omitted. Application of the transmitters to analog systems (e.g., CATV) and digital systems is described.