1844 results about "Multi-mode optical fiber" patented technology

A single-mode optical fiber includes a central core, an intermediate cladding, a depressed trench, and an external optical cladding. The central core has a radius r₁ and a positive refractive index difference Δn₁ with the optical cladding. The intermediate cladding has a radius r₂ and a positive refractive index difference Δn₂ with the optical cladding, wherein Δn₂ is less than Δn₁. The depressed trench has a radius r₃ and a negative index difference Δn₃ with the optical cladding. At a wavelength of 1310 nanometers, the optical fiber has a mode field diameter (MFD) between 8.6 microns and 9.5 microns and, at a wavelength of 1550 nanometers, the optical fiber has bending losses less than about 0.25×10⁻³ dB/turn for a radius of curvature of 15 millimeters. At a wavelength of 1260 nanometers, attenuation of the LP11 mode to 19.3 dB is achieved over less than 90 meters of fiber.

The present wavelength multiplexed optical system includes a multimode optical fiber that transmits wavelength multiplexed optical signals and a plurality of multimode modal dispersion compensation optical fibers. Each modal dispersion compensation optical fiber can transmit one of the multiplex wavelengths, and each modal dispersion compensation optical fiber has an optimized index profile such that the modal dispersion for the transmitted wavelength is approximately inversely equal to the modal dispersion induced in the multimode optical fiber. The wavelength multiplexed optical system facilitates an increased bitrate without reducing bandwidth.

A multimode optical fibre communications system, and in particular to a system in which non-linearities in the propagation of the signal through a multimode optical communications channel degrade the signal presented to the receiver. The system includes an optical transmitter unit for connection to a multimode optical fibre transmission link. The transmitter unit has a data input for receiving an input data signal, a data signal processing circuit and a source of optical radiation. The data signal processing circuit is arranged to receive the input data signal from the data input and to provide a processed data signal to the source of optical radiation and the source of optical radiation is arranged to generate from this an optical signal for transmission by a multimode optical fibre. The data processing circuit is arranged to provide from the input data signal a non-inverted data signal and an inverted data signal, receive a control signal for controlling the generation of the processed data signal, apply a controllable delay in accordance with the control signal to at least one of the non-inverted and inverted data signals, and combine the non-inverted and inverted signals after the application of the controllable delay(s) and gain factor(s) to generate the processed data signal.

Multimode optical fiber is disclosed herein comprising germania and fluorine co-doped in the core of the fiber. The dopant concentration profiles are defined by a pair of alpha parameters. The operating window, or bandwidth window, is enlarged and attenuation, or loss, is low. In some embodiments, two operating windows are available for transmission.

Disclosed is an optical system including a polychromatic optical source emitting multiple transverse modes, an optical link having at least one portion of multimode optical fiber, and an optical device positioned between the optical source and the input of the multimode optical fiber. The optical device can modify the distribution of the energy coupling of the transverse modes emitted by the source in the propagation modes of the multimode optical fiber.

The optical system makes it possible to use low-cost transverse multimode optical sources for producing high-bandwidth Ethernet transmission networks having excellent performance.

An improved fiber-optic communications system comprises a multi-mode waveguide carrying an optical signal, a single-mode waveguide optically coupled to and receiving the optical signal from the multi-mode waveguide and an adiabatic coupler optically coupled between the multi-mode waveguide and the single-mode waveguide. The multi-mode and single-mode waveguides may be optical fibers. The adiabatic coupler may comprise a tapered core surrounded by a cladding. Alternatively, the adiabatic coupler may comprise a core surrounded by a cladding, wherein the refractive index of at least one of the core and the cladding varies over the length of the adiabatic coupler.

An optical fiber that is relatively insensitive to bend loss comprises a core region and a cladding region configured to support and guide the propagation of light in a fundamental transverse mode, the cladding region including (i) an outer cladding region having a refractive index less than that of the core region, (ii) an annular cladding pedestal region having a refractive index higher than that of the outer cladding region and comparable to that of the core region, and (iii) an annular cladding inner trench region disposed between the core region and the pedestal region, the inner trench region having a refractive index less than that of the outer cladding region. In one embodiment, the fiber also includes a (iv) an annular cladding outer trench region disposed between the pedestal region and the outer cladding region, the outer trench region having a refractive index less than that of the outer cladding region. In addition, to suppress HOMs the pedestal region is configured to resonantly couple at least one other transverse mode of the core region to at least one transverse mode of the pedestal region. Such fiber is advantageously used as access fiber, but may have other applications, such as sensor fiber.

A laser utilizes a cavity design which allows the stable generation of high peak power pulses from mode-locked multi-mode fiber lasers, greatly extending the peak power limits of conventional mode-locked single-mode fiber lasers. Mode-locking may be induced by insertion of a saturable absorber into the cavity and by inserting one or more mode-filters to ensure the oscillation of the fundamental mode in the multi-mode fiber. The probability of damage of the absorber may be minimized by the insertion of an additional semiconductor optical power limiter into the cavity. To amplify and compress optical pulses in a multi-mode (MM) optical fiber, a single-mode is launched into the MM fiber by matching the modal profile of the fundamental mode of the MM fiber with a diffraction-limited optical mode at the launch end, The fundamental mode is preserved in the MM fiber by minimizing mode-coupling by using relatively short lengths of step-index MM fibers with a few hundred modes and by minimizing fiber perturbations. Doping is confined to the center of the fiber core to preferentially amplify the fundamental mode, to reduce amplified spontaneous emission and to allow gain-guiding of the fundamental mode. Gain-guiding allows for the design of systems with length-dependent and power-dependent diameters of the fundamental mode. To allow pumping with high-power laser diodes, a double-clad amplifier structure is employed. For applications in nonlinear pulse-compression, self phase modulation and dispersion in the optical fibers can be exploited. High-power optical pulses may be linearly compressed using bulk optics dispersive delay lines or by chirped fiber Bragg gratings written directly into the SM or MM optical fiber. High-power cw lasers operating in a single near-diffraction-limited mode may be constructed from MM fibers by incorporating effective mode-filters into the laser cavity. Regenerative fiber amplifiers may be constructed from MM fibers by careful control of the recirculating mode. Higher-power Q-switched fiber lasers may be constructed by exploiting the large energy stored in MM fiber amplifiers.

The invention provides a monomode optical fiber having, at a wavelength of 1550 nm: an effective section area greater than or equal to 60 mum2; chromatic dispersion close to 8 ps/(nm.km); a chromatic dispersion slope of absolute value less than 0.07 ps/(nm2.km). In the range of wavelengths used in a WDM transmission system, typically 1530 nm to 1620 nm, the fiber has chromatic dispersions greater than 7 ps/(nm.km), thereby making it possible to limit non-linear effects. The invention also provides a WDM optical fiber transmission system using such a fiber as a line fiber. The small slope of its chromatic dispersion is an advantage in such a system.

An optical coupler is provided. It has a bundle of multimode fibers with a few-mode fiber in its centre. Such bundle is fused at one end which is the output end for the signal that is transmitted by the few-mode fiber. To make the coupler, this output end of the bundle is aligned and spliced with a large area core double clad fiber while preserving the modal content of the feed-through. A method for making such optical coupler is also provided. It includes the steps of bundling a central few-mode fiber with a plurality of multimode fibers and then fusing one end of such bundle and aligning it and splicing with a large core double clad fiber, while preserving fundamental mode transmission from one to the other.

A multimode long period fiber Bragg grating (LPFBG) for a predetermined wavelength band. The LPFBG formed of a non-photosensitive material having an initial index of refraction. The multimode optical fiber core includes a substantially cylindrical surface, a longitudinal core axis, a core radius, and a number of index-altered portions having an altered index of refraction different from the initial cladding index of refraction. Each of the index-altered multimode optical fiber core has a first transmission surface and second transmission surface that is substantially parallel to the first transmission surface. Also, these index-altered portions are arranged within the non-photosensitive material of the multimode optical fiber core such that the first transmission surface of one portion of the plurality of index-altered portions is substantially parallel to the second transmission surface of a neighboring portion to form a long period Bragg grating structure.

A bend-loss tolerant multimode fiber transmission system is provided. The system includes: a transmission fiber having a core and a cladding, and a mode-launching system for selectively exciting only a useful portion of the transmission modes, that portion corresponding to high effective refractive indices relative to a refractive index of the cladding the useful portion corresponding to a substantial number of modes. The mode-launching system may include a lead-in fiber, coupled to the transmission fiber, supporting a number of lead-in modes substantially corresponding to the number of transmission modes in the useful portion. The transmission fiber may have a refractive index profile, within a region of its core that is aligned with the lead-in fiber core, which has a shape that matches a refractive index profile shape in the lead-in fiber core. The transmission fiber core may have a graded refractive index profile that is parabolic or nearly parabolic or truncated.

A two-channel fiber optical rotary joint has been invented in which optical signals can be transmitted simultaneously along two optical passes through a single mechanical rotational interface for both single mode fiber and multi mode fiber. The first channel of light path consists of a pair of micro-collimators, or a pair of fibers, co-axially fixed in 2 holders respectively. The light signal from one of micro-collimator, or fiber can be directly coupled into another micro-collimator, or fiber. The second channel of light path is off-axis arranged, including a pair of conventional collimators, a pair of first reflecting surfaces and a pair of second reflecting surfaces. The light signal emitted from one of the said conventional collimator will be reflected by one of the said first reflecting surface, one of the said second reflecting surface, another said second reflecting surface, and another said first reflecting surface, then coupled into another said conventional collimator. An index matching fluid is filled in the housing for lubrication and pressure compensation purposes.

A fiber-optic bundle based optical coherence tomography (OCT) probe method is demonstrated in a multimode optical fiber bundle based OCT system. The system can achieve a lateral resolution of 12 μm and an axial resolution of 10 μm using a super-luminescent diode source. This imaging approach eliminates any moving parts in the probe and has a primary advantage for use in extremely compact and safe OCT endoscopes to image internal organs and great potential to be combined with confocal endoscopic microscopy.

The specification describes multimode optical fibers with specific design parameters, i.e., controlled refractive index design ratios and dimensions, which render the optical fibers largely immune to moderately severe bends. The modal structure in the optical fibers is also largely unaffected by bending, thus leaving the optical fiber bandwidth essentially unimpaired. Bend performance results were established by DMD measurements of fibers wound on mandrels vs. measurements of fibers with no severe bends.

A multimode to low-mode optical fiber is constructed by forming a plurality of multimode optical fibers into a fiber bundle. The bundle is then selectively heated and drawn to form a bi-tapered fiber bundle having a central straight portion in which the multimode fibers are fused into a single length of fiber. During the drawing step, measures are taken to provide an aperture extending through the bi-tapered bundle, including the single straight portion of the bundle. An optical fiber having a low-mode or single-mode core is inserted through the aperture into the straight section of the bi-tapered bundle. The bi-tapered bundle and the low-mode core fiber are heated to a temperature at which cladding of the low-mode core fiber fuses to the straight portion of the bi-tapered bundle. The bi-tapered bundle is then cleaved in the straight portion to provide the multimode to low-mode optical fiber combiner. In one example, the multimode fiber bundle is formed around a metal wire before the drawing operation. After the drawing operation the wire is extracted from the bi-tapered bundle leaving the aperture in the bi-tapered bundle.

The invention relates to a low-attenuation single mode optical fiber used in an optical fiber communication system. The single mode optical fiber comprises a core layer and a wrapping layer. The single mode optical fiber is characterized in that the refractive index distribution n (r) of the core layer and the g-type refractive index distribution of the core layer meet the formula: n (r)=n0*[1-2*delta 1*(r/R1)*g]*1/2 (r<=R1), the delta 1 of the core layer ranges from -0.05% to +0.05%, g ranges from 10 to 30, and the radius R1 of the core layer ranges from 4.0 microns to 5.0 microns; the wrapping layer sequentially comprises an inner wrapping layer, a middle wrapping layer and an outer wrapping layer from inner to outer, the delta 2 of the inner wrapping layer ranges from -0.3% to -0.45%, the radius R2 ranges from 20 microns to 30 microns, and the delta 3 of the middle wrapping layer is larger than delta 2, the numerical relationship between the relative refraction difference and the radius of the middle wrapping layer and the relative refraction difference and the radius of the inner wrapping layer is V=(R3-R2)*(delta 3-delta 2), and V ranges from 0.5*10-2-micron% to 7*10-2-micron%. The attenuation coefficient, at the 1550-nanometer position, of the optical fiber is smaller than or equal to 0.180dB/km. The low-attenuation single mode optical fiber is low in optical fiber loss, good in manufacturing technology, low in cost and suitable for scale production.