We present novel optical fiber designs to improve performance of distributed optical fiber sensors based on Rayleigh and Brillouin scatterings, including hybrid core fiber for increasing Rayleigh backscattered signal, dual core fiber for simultaneous measurement of temperature and stain, few mode fiber for enhancing sensitivity and spatial resolution and Brillouin frequency managed fiber for increasing sensing range.
Ying Geng, Shenping Li, Ming-Jun Li, Clifford Sutton, Robert McCollum, Randy McClure, Alexander Koklyushkin, Karen Matthews, James Luther, Douglas Butler
A complete single mode dual-core fiber system for short-reach optical interconnects is fabricated and tested for high-speed data transmission. It includes dual-core fibers capable of bi-directional data transmission, dual-core simplex LC connectors, and fan-outs. The transmission system offers simplified bi-directional traffic engineering with integrated bidirectional transceivers and compact system design, utilizing simplex dual-core LC connectors that use half the space while increasing the bandwidth density by a factor of two. The fiber has two cores that are compatible with single mode fiber and conforms to the industry standard outer diameter of 125 μm. This reduces operational complexity by reducing the size and number of fibers, cables and connectors. Measured OTDR loss for both cores was 0.34 dB/km at 1310 nm and 0.19 dB/km at 1550 nm. Crosstalk for a piece of 5.8 km long dual-core fiber was measured to be below -75 dB at 1310 nm, and below -40 dB at 1550 nm. Both free-space optics fan-outs and tapered-fiber-coupler based MCF fan-outs were evaluated for the transmission system. Error-free and penalty-free 25 Gb/s bi-directional transmission performance was demonstrated for three different fiber lengths, 200 m, 2 km and 10 km, using the complete all-fiber-based system including connectors and fan-outs. This single mode, dual-core fiber transmission system adds complementary value to systems where additional increases in bandwidth density can come from wavelength division multiplexing and multiple bits per symbol.
We demonstrate a frequency-converted green laser source simultaneously emitting three spectral lines with nearly equal
intensity and ~ 0.5 nm separation, enabling a factor of √3 reduction of speckle contrast in pico-projector applications.
The source consists of an external cavity 1060 nm diode laser pump with dual-wavelength reflection provided by a
volume Bragg grating and a quasi-periodically poled MgO-doped lithium niobate waveguide engineered to phase-match
multiple-wavelength frequency conversion. 62 mW output power and 33% conversion efficiency are demonstrated.
A novel room-temperature multi-wavelength erbium-doped fiber ring laser is proposed. In this laser, four-wave
mixing (FWM) is used to mitigate mode competition, achieving stable room-temperature multi-wavelength operation.
Active mode-locking is incorporated to enhance the FWM effect, improving the amplitude flattening and spectral
bandwidth of the multi-wavelength output. Stable simultaneous 42 wavelength lasing operation with 0.55 nm
wavelength spacing within the 3 dB spectral band is experimentally demonstrated.
In this paper, we studied SC generation in fiber lasers and in optical fibers pumped by different
light sources which include fs and ps pulse sources, and continuous-wave (CW) amplified spontaneous
emission (ASE) light sources. First, we demonstrated SC generation with a 10dB spectral bandwidth of
430nm in a fiber ring laser with conventional nonlinear fiber. Second, we proposed and demonstrated a
new and efficient approach to generation of a CW SC in optical fibers pumped by a CW ASE light. A
bandwidth of 268nm (at -15dB level) with an average spectral density of 2.7mW/nm was
demonstrated. Various approaches to flattening the spectrum and increasing the spectral width were
also studied. The application of this SC source in WDM passive optical access networks (WDM-PONs)
was investigated. Third, the approach of SC generation in a fiber combination of standard SMF
and nonlinear DSF pumped by an all-fiber fs pulse Master Oscillator Power Amplifier (MOPA) system
was developed. A spectral bandwidth of over 1000nm was demonstrated. Finally, the generation of
broad comb-like-spectral light based on the pulse compression of 40GHz optical pulses in a new
nonlinear dispersion-decreasing fiber with high SBS threshold was studied. A continuum light source
with over 125 channels and a channel spacing of 40 GHz was achieved. The use of this continuum light
source as WDM source in WDM-PONs was investigated.
This paper reviews silica glass based nonlinear optical fiber designs for signal processing using optical Kerr effect. The requirements for designing nonlinear fibers are described first. Then the design concept is discussed and design examples are shown to illustrate the tradeoffs among the different fiber properties such as effective area, dispersion and attenuation. Furthermore, fiber designs with distributed Brillouin frequency shift to mitigate the effect of simulated Brillouin scattering in nonlinear fibers are discussed in detail. SBS threshold increase of 7 dB over conventional nonlinear fibers is experimentally demonstrated.
Without using any additional SBS suppression means, 40 GHz 33% RZ pulse train generated by external modulation of a DFB laser diode output was successfully compressed to high-quality 1.3 ps transform-limited soliton pulses using adiabatic soliton compression in 5.45 km long DDF with high SBS threshold. Using the same fiber, as short as 870 fs low-pedestal soliton pulses were produced by higher-order soliton pulse compression.
We report a self-starting stretched-pulse mode-locked all-fiber erbium ring laser with high output pulse energy. In this laser, to increase the output pulse energy a piece of positive-dispersion singlemode fiber with large core diameter is used to lower the nonlinearity in the positive dispersion section of the laser cavity. Pulses with ~0.6 nJ single-pulse energy and less than 100 fs was achieved.
Dynamic dispersion compensation based on non-linear self-phase modulation (SPM) in an all-fiber device is demonstrated. The basic design of the compensator is very simple, consisting only of a pre-compensating negative dispersion fiber, an optical amplifier, and a highly non-linear positive dispersion fiber. Multiple channel operation of the compensator is feasible and experimentally demonstrated. An increase of dispersion tolerance of at least a factor of 2 is shown with low penalty of less than 2 dB. Finally, device performance in a 2000 km fiber loop experiment is presented.
A simple method for achieving fast wavelength switching in a fiber laser was demonstrated using a Fabry-Perot semiconductor filter and a set of fiber Bragg gratings. A build-up time as short as 1.6microsecond(s) was obtained.
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