Fiber Grating Laser Research Articles

Magnetostrictive composite material-based polarimetric heterodyning fiber-grating laser miniature magnetic field sensor

A novel fiber-optic magnetic field sensor is demonstrated based on a dual-polarization fiber-grating laser, which is embedded in an epoxy resin-bonded magnetostrictive composite material with doped Terfenol-D particles. A simple structure is designed to convert the magnetic field-induced strain to transversal stress, which is applied to the fiber laser to produce beat note frequency changes for measurement purposes. The response of the proposed sensor is measured, and shows quite a good directivity and linearity with a sensitivity of 10.5 Hz/?T to the magnetic field. It also shows a large measurable range up to about 0.3 T.

대신호 시영역 모델을 이용한 광섬유 격자 외부 공진 레이저 다이오드의 해석

A large-signal time-domain model is implemented to analyze an FG-LD (Fiber Grating Laser Diode) in which a reflective laser diode is hybrid-integrated with a fiber Bragg grating (FBG). When the length of the externally integrated resonator is 8 mm, in which the effective FBG length of 2.1 mm is included, a static frequency chirp of 0.44 GHz and a dynamic frequency chirp of 6.4 GHz are observed. In addition, it is also observed that the eye of the 10Gbps NRZ signal is well open. The FG-LD is expected to be a cost-effective solution for a 10Gbps-class single wavelength laser covering a span of 50 km range.

Fiber Grating Laser Current Sensor Based on Magnetic Force

A novel fiber-optic current sensor based on a dual-polarization fiber grating laser is proposed and experimentally demonstrated. A permanent magnet exerts transversal force to the dual-polarization fiber grating laser due to the action of a magnetic field produced by an electric current. The transversal force modulates the fiber birefringence and, therefore, the beat frequency between the two polarization modes from the fiber grating laser. The sensor is capable of measuring both dc and ac current, and has advantages of ease of interrogation, absolute frequency encoding, and capability to multiplex a number of sensors on a single fiber.

Dynamics of ultimate spectral narrowing in a semiconductor fiber-grating laser with an intra-cavity saturable absorber

The ultimate spectrum-narrowing and side-mode suppression due to the presence of a saturable absorber in an external cavity of a fiber Bragg grating semiconductor laser is numerically simulated. The proposed algorithm describes an effect of absorption bleaching in a saturable absorber using earlier measurements and shows the evolution of a dynamic grating in the laser cavity. The simulations confirm for the first time an empirical theory of spectral line narrowing in a laser with an intra-cavity saturable absorber.

Fiber grating laser: a performance study on coupling efficiency of fiber microlens and the Bragg reflectivity

The λ=1.55 μ m fiber grating lasers (FGLs), comprised of an uncoated tapered hemispherical-end fiber (THEF) microlens for strong coupling the fiber grating external cavity and the HR/AR-coated diode laser, have been investigated in four different combinations of coupling efficiency ( η) and Bragg reflectivity ( R g). The FGL of higher η=72% and R g=0.52 has a stronger resonant feedback as the spectral output shows a single longitudinal mode (SMSR>45 dB), high output power (>5 mW), and lower threshold current. However, for the case of R g=0.35 and η=68%, the FGL exhibits more stable SMSR against pumping current and temperature. We have also performed numerical simulation on the SMSR at different η and R g for the FGLs. The calculated SMSR shows an excellent agreement with the measured data for the FGLs of higher η.

1.55-µm Fiber Grating Laser Utilizing an Uncoated Tapered Hemispherical-End Fiber Microlens

An uncoated tapered hemispherical-end fiber microlens, formed by etching a single-mode fiber in a hydroflouride solution, is spliced with a fiber grating to form an external cavity for a 1.55 µm fiber grating laser (FGL). The fiber microlens provides a coupling efficiency of more than 65% between the semiconductor laser and the fiber grating external cavity. The FGL has spectral characteristics of a single line (λ0=1555.6 nm), a single longitudinal mode (SMSR>30 dB), and a high output power (>1 mW). However, the SMSR shows a current-dependent oscillation, which can be consistently explained by calculating the rate equations of an equivalent external cavity model on the FGL.

1.55-μm non-anti-reflection-coated fiber grating laser for single-longitudinal mode operation

A 1.55-μm fiber grating laser (FGL) was fabricated by optically packaging a non-anti-reflection (AR) coated Fabry–Perot (FP) laser to a lensed fiber grating. The FGL demonstrates a single-longitudinal mode operation with a side-mode suppression ratio (SMSR) of up to 40 dB. The SMSR oscillates and diminishes to <30 dB as the increase of injection current above 38 mA, and the tilt of the fiber approaches ∼5° away from the facet normal of the FP laser. We have performed numerical simulations on the single-longitudinal mode operation for the FGL. The SMSR for the FGL increases over 40 dB as the increase of the fiber grating reflectivity (Rg) above 0.7 with non-AR-coated FP laser facet. Our calculations also show that the strong current-dependent SMSR oscillation is from the mode selection by the fiber grating external cavity and the heating effect in the FP laser.

Fibre grating laser-based RZ pulse source for 40Gbit/s OTDMtransmission systems

The performance of an actively modelocked fibre grating laser (FGL) used to generate near-transform-limited pulses (/spl Delta/v/spl Delta//spl tau/=0.5-0.65) with FWHM of 12-18 ps at 10 GHz repetition rate is described. 40 Gbit/s OTDM experiments using the modelocked FGL as a pulse source yielded less than 1 dB power penalty with respect to a 10 Gbit/s RZ signal.

Short-Cavity Er/Yb-P/Al/Si Co-doped Fibre Grating Laser

A short-cavity Er/Yb-P/Al/Si co-doped fibre grating laser isdemonstrated, with a pair of fibre Bragg gratings whose central resonantwavelengths are around 1551 nm and the reflectivities are 10.5 and 15 dB.The threshold value is about 48 mW and the slopeefficiency is 1.1%. The signal-to-noise ratio is 59 dB, and the outputcentral wavelength is 1550.94 nm. A peak power of 1.112 mW at apump power of 80 mW has been achieved.

L-band erbium-doped fiber amplifier incorporating an inline fiber grating laser

Wide-band erbium-doped fiber amplifiers (EDFAs) having an inherently flat gain spectrum in the long-wavelength-band (L-band) between 1570 nm and 1600 nm have recently been realized. The L-band amplification has been achieved by simply using a longer length of EDF than in the conventional-wavelength-band (C-band) EDFAs. In the paper, we investigate the improvement of the gain flatness in an L-band EDFA co-pumped with the high-power pump light at 1.48 /spl mu/m and the medium-power auxiliary pump light at 1.55-1.565 /spl mu/m. We also propose a novel L-band EDFA incorporating an inline fiber grating laser (FGL) operating at the auxiliary pump wavelength, and demonstrate that the proposed EDFA has better gain flatness as well as the gain clamping characteristics.

Fabrication of High-Power Fiber Grating Laser and Its Performance.

We theoretically considered suitable configurations of a fiber grating laser (FGL) to be used in wavelength division multiplexing (WDM) systems. We focused on the effect of composite reflectors where the effect of the front facet of a semiconductor optical amplifier (SOA) is especially significant. We simulated relaxation oscillation frequency and optical power to determine a configuration enabling high bit rates, up to 2.5 Gbit/s. After arriving at a suitable configuration, a packaged FGL has been fabricated. This laser achieves higher output power than any previously reported, and the potential for a rate of 2.5 Gbit/s was confirmed. Compared with a typical 1.55 μm MQW DFB laser, the lasing wavelength temperature dependence is less than half that of a DFB laser. As frequency chirping is remarkably reduced, the power penalty of the FGL is 3 times smaller than that of a DFB laser in transmission experiment with SMF of 70 km.

Fabrication of High-Power Fiber Grating Lasers for Wavelength Division Multiplexing Systems and their Fundamental Performance.

We fabricated Fiber Grating Lasers (FGLs) which consist of a Strained-LayerMultiple-Quantum-Well Semiconductor Optical Amplifier (SL MQW SOA) and an externally distributed Fiber Bragg Grating (FBG) reflector to evaluate its potential for use in Wavelength Division Multiplexing (WDM) systems.By using 600μm long SL MQW SOAs, the fiber output power through an inline isolator is higher than 15 mW at 100 mA at 20 to 30°C To the best of our knowledge, our resulting level of performance is higher thanany previously reported. On the other hand, the limit of data rates is specified with relaxation frequency.In order to achieve high bit rates, a Bragg grating is positioned beside a lensed fiber end to obtain shorter cavity length. The lasers achieve 2.5 Gbit/s direct intensity modulation, according to evaluated relaxation frequency.We demonstrate this fabrication process and the fundamental performance of the packaged laser. These lasershave great potential for use in wavelength-specified, wavelength-stabilized, high-power, low-noise, andlow chirping WDM transmitters.

Fibre optic tunable transversal filter using laserarray andlinearly chirped fibre grating

The authors present an experimental demonstration of a fibre optic tunable transversal filter using a single linearly chirped fibre grating and tunable laser array to control the time delay.

Long-Term Bit Error Rate Transmission Using an Erbium Fiber Grating Laser Transmitter at 5 and 2.5 Gb/s

We report the successful use of a 1540-nm erbium fiber grating (EFG) laser as a stable transmitter source in long-term bit error rate (BER) transmission fiber experiments at 5 and 2.5 Gb/s. At 5 Gb/s, straight BER performance results in error-free operation for 3 days of the system through 86 km of non-dispersion-shifted fiber. Also, there is no degradation in the receiver sensitivity (-21 dBm at BER 10 -10) whether the system is operated with the EFG laser or a distributed feedback laser. At 2.5 Gb/s, stable transmission performance with BER below 10 -13 (-32.5 dBm) is demonstrated over 300 km of standard single-mode fiber in a chain of four equally spaced 980-nm-pumped erbium-doped fiber amplifiers. These results indicate that the EFG laser is a promising candidate for long-distance high-speed transmission applications.

Stable single-mode erbium fiber-grating laser for digital communication

In this paper we report the fabrication of a short, robust, single-mode Er/sup 3+/ fiber-grating laser. This laser is proven by the successful outcome of a long-term bit-error-rate test at the 10/sup -15/ level in a 5- G/s fiber transmission experiment. In the process we present a new pumping geometry, the elucidation of one origin of relaxation oscillations that have plagued previous lasers and the demonstration of a simple electronic feedback scheme for suppressing them. This prototype source shows real promise for use in a high-speed communications system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>