Ofs Fitel, LLC

Lucent Technologies Inc.

Fitel USA Corporation

Ofs Fitel Llc, a Delaware Limited Liability Company

Clifford E Headley

David John DiGiovanni

Benjamin John Eggleton

Lalitkumar Bansal

Stephen G Grubb

Thomas Andrew Strasser

Kenneth L Walker

Man Fei Yan

Jeffrey W Nicholson

William Alfred Reed

Per Bang Hansen

Lars Erik Eskildsen

Marc Mermelstein

Bennett H Rockney

Jerome C Porque

Paul Steinvurzel

Jane B Clayton

Stephan Wielandy

Martin H Muendel

Janet Renee Pedrazzani

Jake Bromage

Khushvinder Brar

Jean-Christopher Bouteiller

Akheelesh Abeeluck

David J Digiovanni

Andrea Rosales-Garcia

Abds-Sami Malik

Jean-Christophe Bouteiller

An all-glass cladding mode stripper comprises a plurality of high refractive index, small diameter glass beads disposed along an exposed portion of the inner cladding region of an optical fiber. The unwanted low NA signal light (as well as any other type of stray light) propagating within the cladding layer is removed by refracting into the adjacent beads, where this captured light then scatters away from the optical fiber.

Cladding mode stripper for use with optical systems and methods of forming the same

An optical gain fiber for use in high power (e.g., greater than 500 W pump power) is proposed that is configured to exhibit a minimum bend radius such that the bend loss for the propagating LPmode is greater than about 0.03 dB/m. It has been discovered that this bend radius criteria, which is less stringent than that typically suggested in the art (e.g., bend loss less than about 0.03 dB/m), meets the modal stability requirements at high power operation, since the increase in operating temperature of the fiber laser or amplifier has been found to somewhat relax the bend radius requirement (which was heretofore only measured at 'room temperature', not 'operating temperature'). Modal stability is defined in terms of a reduced presence of unwanted higher-order modes (such as the LPmode) in the amplified output signal.

Gain fiber for high power lasers and amplifiers

A high efficiency optical combiner minimizes core region distortions in the area where fusion splicing between an input tapered fiber bundle (or any other type of 'cladding-less' input fiber) and output fiber are joined. The thickness of the output fiber's glass cladding layer in the splice region is reduced (if not removed altogether) so that a core-to-core splice is formed and any necked-down region where the glass flows to join the core regions (while also joining the outer diameters) is essentially eliminated. The reduction of distortions in the core region of the splice improves the transmission efficiency between an input tapered fiber bundle and output fiber, reaching a level of about 99%. This high efficiency optical combiner is particularly well-suited for applications where a number of pump sources are combined and applied as an input to a fiber laser or amplifier.

High efficiency pump signal combiner for high power fiber amplifier and laser applications

A light generation and amplification system includes a length of laser-active filter fiber having a refractive index profile that suppresses unwanted Stokes orders at wavelengths longer than a target wavelength and that has normal dispersion over its operating wavelength. A nested series of reflectors is provided at the fiber's input and output ends, and are configured to provide a nested series of Raman cavities, separated in wavelength by approximately the respective Stokes shifts. The first cavity in the series is a combined cavity that provides laser oscillation due to a combination of ionic gain and feedback at a selected first wavelength and that provides Raman gain to light at the first Stokes shift of the first wavelength when light at the first wavelength has an energy exceeding a Raman scattering threshold. The Raman cavities provide a stepwise transition between the first wavelength and the target wavelength.

Cascaded raman fiber laser system based on filter fiber

Optical apparatus includes a multimode, gain-producing fiber for providing gain to signal light propagating in the core of the fiber, and a pump source for providing pump light that is absorbed in the core, characterized in that (i) the pump source illustratively comprises a low brightness array of laser diodes and a converter for increasing the brightness of the pump light, (ii) the pump light is coupled directly into the core, and (iii) the area of the core exceeds approximately 350 &#x3bc;m. In one embodiment, the signal light propagates in a single mode, and the pump light co-propagates in at least the same, single mode, both in a standard input fiber before entering the gain-producing fiber, and a mode expander is disposed between the input fiber and the gain-producing fiber. In another embodiment, multiple pumps are coupled into the core of the gain-producing fiber. The pumps may generate light of the same wavelength or of different wavelengths. In accordance with a particular embodiment of our invention, we have demonstrated amplification of nanosecond optical pulses at 1545 nm in a single clad Er-doped fiber having a core area of 875 &#x3bc;m; the core was pumped by a high brightness Raman laser at 1480 nm; and the pulses had a record peak power of several hundred kW.

High power optical apparatus employing large-mode-area, multimode, gain-producing optical fibers

A filled-core optical fiber and method where the optical fiber is collapsed at opposing ends subsequent to the active optical material being introduced into the hollow core region. The collapsing-functions to &ldquo;pinch off&rdquo; the active material (which may be a liquid or solid) within the fiber structure and also collapse the cladding layer ring surrounding the core into a solid core region on either side of the active material. The filled-core fiber is then sealed and can be coupled to standard fiber using conventional splicing processes.

Filled-core optical fiber and method of making the same

A multi-wavelength cascaded Raman resonator (&ldquo;MWCRR&rdquo;). The MWCRR has an optical source for pumping optical radiation centered around an input wavelength. The MWCRR further includes a Raman fiber having at least a first set of optical gratings for converting the pumped optical radiation to wavelengths other than the input wavelength. The Raman fiber also has at least one adjustable output coupler having a variable reflectivity for controlling the power of the optical radiation propagating from the at least one set of optical gratings at the wavelengths other than the input wavelength.

Multiwavelength cascaded raman resonator

The specification describes a distributed Raman amplifier with multiple pump sources for wide band amplification of wavelength division multiplexed (WDM) signals. It was recognized that using multiple pump sources introduces non-linear effects, such as four wave mixing (FWM). These effects are reduced by multiplexing the pump wavelengths in the multiple pump source. It was also recognized that not all of the pump wavelengths over the wavelength spectrum of the pumps contributes to FWM. Thus fewer than all of the pump wavelengths require multiplexing to eliminate FWM in the multiple wavelength pump source. Various approaches are described to ensure that the pump wavelengths do not interact in FWM in the transmission span. The selected individual pump wavelengths may be either time division multiplexed, or frequency modulated.

Wide band Raman amplifiers

In accordance with the invention, an optical fiber communication system comprising a source of optical signal channels and an optical fiber transmission line is provided with one or more single source, multiple-order Raman pumps downstream of the source. Each single source pump provides multiple-order Raman pump light for amplifying the signal channels.

Single-source multiple-order raman amplifier for optical transmission systems

At least some rare earth-doped optical fiber lasers are subject to self-pulsing and/or relatively high noise. We have found that these shortcomings can be eliminated if the cavity length of the fiber laser is increased, typically by inclusion of a length .LAMBDA. of rare earth-free conventional (single mode) transmission fiber in the cavity, with .LAMBDA.&gt;0.3L, where L is the effective cavity length of the laser.

Article comprising an improved rare earth-doped optical fiber laser

In accordance with the invention, a Ge-doped optical fiber having reduced Brillouin scattering loss is made by modulating the tension applied to the fiber during draw. The draw tension is modulated between a low range 10-50 g and a high in the range 150-250 g. The result is SBS suppression with no significant change to end-to-end fiber loss or dispersion factors.

Method for making Ge-Doped optical fibers having reduced brillouin

Applicants have discovered that the intermodal beat noise of a fiber multimode laser can be substantially reduced by providing the fiber with an output coupler of broadened bandwidth. In a preferred embodiment, a reduced-noise, high power light source comprises a cladding pumped fiber laser having a chirped output grating. Experiments show that increasing the output bandwidth from 0.254 to 0.577 nm reduces the relative intensity-to-noise ratio 10 dB in a Nd-doped fiber laser. Increasing the bandwidth from 0.2 nm to 0.3 nm in a Yb-doped laser similarly reduces the noise by 12 dB.

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Flemington, NJ, United States of America

Clifford E Headley