Broadband Fiber Bragg Grating Research Articles

Single-frequency erbium-doped fiber laser based on self-injection feedback

In this paper, a single-frequency erbium-doped fiber laser based on self-injection feedback is reported, which uses a high-reflectivity broadband fiber Bragg grating, an ordinary commercial high-doped erbium fiber and a low-reflectivity broadband fiber Bragg grating to form the main resonant cavity, and a stable narrow linewidth single-frequency laser output is achieved by connecting a single-mode fiber and a low reflectivity narrowband fiber Bragg grating to form self-injection feedback. Then, a saturated double-pass erbium-doped fiber amplifier and a saturable absorber were added to the self-injection optical path, which well suppressed the relative intensity noise and phase noise and the relaxation oscillation intensity was well suppressed by about 18.08 dB, and the phase noise was 36.7dBc·Hz−1 suppression, the edge-mode rejection ratio is increased by 13 dB, and the final laser linewidth is about 270 Hz, and the output power is 8.5 dBm.

Tunable gain clamping L-band erbium-doped fiber amplifier based on FBG and BBM

An improved structure for the L-band Erbium-doped fiber amplifier (EDFA) with gain clamping is suggested to address gain instability resulting from variations in the number of optical channels and the compromised gain clamping performance due to misalignment in the center wavelength of the grating. Here, a linear resonant cavity is formed by a broad-band mirror (BBM) and fiber Bragg grating (FBG), and a variable optical attenuator (VOA) is used for cavity loss adjustment. Experimental results show that the L-band EDFA solves the problem that the center wavelength of the narrowband grating pairs needs to be consistent. The 20 dB gain bandwidth is 42 nm(1582 ∼ 1623 nm). For signal at 1605 nm, the gain can be tuned from 28.8 to 34.8 dB, and a 40 dB (−50 to −10 dBm) gain clamped dynamic range is obtained at the gain of 28.8 dB, with stability of ± 0.25 dB, for which noise figure (NF) is less than 5.3 dB.

Broadband and High Sensitivity FBG Accelerometer Based on Double Diaphragms and h-Shaped Hinges

A novel broadband and high sensitivity fiber Bragg grating (FBG) accelerometer is designed and analyzed. The accelerometer is based on a compact structure consisting of double diaphragms and h-shaped hinges. The h-shaped hinge structure is used to break through the restriction between sensitivity and resonance frequency. The FBG accelerometer is demodulated by an interferometric method and test results show that the acceleration sensitivity is 32 dB re pm/g between 1 Hz and 1 kHz, with a fluctuation less than ±3 dB, and the resonant frequency is above 1.6 kHz. The cross-sensitivity is less than -26 dB in the flat frequency of 15μg/√ Hz in a wide frequency range, making it promising range. The sensor shows a high acceleration resolution for cross-well seismic, micro-seismic monitoring and electromechanical equipment vibration monitoring, etc.

Scanned-wavelength intra-cavity QEPAS sensor with injection seeding technique for C2H2 detection

A high sensitivity scanned-wavelength intra-cavity quartz enhanced photoacoustic spectroscopy (QEPAS) system, based on injection seeding technique and Q-switched technique, was proposed in this paper. In this system, the gas cell was placed in the acousto-optic Q-switched fiber laser cavity, and the high power Q-switched pulses were used to acoustic wave excitation. A distributed feedback (DFB) diode laser with a wavelength scanning range from 1532.63 nm to 1533.03 nm was used as the seed laser to select the laser wavelength. The laser power emitted by the seed laser operating at an injection current of 56 mA (the gas absorption peak) was 3 mW. A custom-made broadband fiber Bragg grating (FBG) with a bandwidth of 500 pm (picometer) was used to stabilize the cavity operation and suppress the amplified spontaneous emission (ASE) spectrum. With an intra-cavity peak pulse power of 0.88 W, the system achieved a minimum detection limit (MDL) of 507 ppbv at atmospheric pressure and room temperature, corresponding to a normalized noise-equivalent absorption (NNEA) of 1.616 × 10−8 W cm−1 Hz−1/2.

Fiber Optic Dual-Ring Michelson Interferometer-Based Detection Scheme for the Measurement of Dynamic Signals

A fiber optic dual-ring Michelson interferometer (DRMI) based detection scheme for the measurement of dynamic signals is proposed and experimentally demonstrated. The fiber optic sensor is a single mode fiber between two broadband fiber Bragg gratings (FBGs) with different center wavelengths. The two FBGs are connected to two output ports of a 3 × 3 coupler to compose a DRMI. High responsivity and wide frequency response range can be achieved at the same time. The scheme has high reliability, in which the undesirable external perturbation applied to interferometric arms is removed. A DRMI-based vibration sensor and a DRMI-based acoustic sensor are fabricated and experimentally investigated. For the DRMI-based vibration sensor, a responsivity of minimum detectable acceleration is 54 μg/√Hz at 300 Hz. The 12.8 rad/g is obtained, and the resonant frequency is 825 Hz. The acoustic sensor is used to detect signals in the frequency range of 0.5-19 kHz. The detection scheme has properties of wide frequency response range, high responsivity, and high reliability.

High-resolution fiber Bragg grating sensor and its applications of geophysical exploration, seismic observation and marine engineering

With the development of fiber Bragg grating (FBG) and FBG based resonant cavity writing and signal demodulation technique, the measurement precision and frequency bandwidth of FBG sensor continue to be improved. It can highly promote its application in several fields of high precision detection requirements, such as geophysical exploration, seismic observation and marine observation. At present, the development of high-precision and wide bandwidth FBG sensors still face some challenges of key devices and techniques, including high-fineness FBG based resonant and low-noise narrow-linewidth tunable laser, high-precision broadband FBG wavelength demodulation technique, large-scale networking technique and high-sensitivity signal pickup probe design. Firstly, this paper introduces the development of high-precision FBG sensing technique. Secondly, it focuses on the cord devices and key techniques required for high-precision FBG sensing system and their applications in geophysical exploration, seismic observations and ocean observations. Finally, the high-precision FBG sensing technique and its application are prospected. In order to provide references for the development and application of high-precision fiber Bragg grating sensing technology, this paper aims to analyze and summarize some of the core techniques involved in high-precision FBG sensing technique and its application and the key issues that need to be solved.

Direct infrared femtosecond laser inscription of chirped fiber Bragg gratings.

We compare and contrast novel techniques for the fabrication of chirped broadband fiber Bragg gratings by ultrafast laser inscription. These methods enable the inscription of gratings with flexible period profiles and thus tailored reflection and dispersion characteristics in non-photosensitive optical fibers. Up to 19.5 cm long chirped gratings with a spectral bandwidth of up to 30 nm were fabricated and the grating dispersion was characterized. A maximum group delay of almost 2 ns was obtained for linearly chirped gratings with either normal or anomalous group velocity dispersion, demonstrating the potential for using these gratings for dispersion compensation. Coupling to cladding modes was reduced by careful design of the inscribed modification features.

An Efficient Photonic Crystal Fiber-Based Brillouin Erbium Fiber Laser Using a Fiber Bragg Grating for Multi-Wavelength Generation

An efficient multi-wavelength Brillouin erbium fiber laser is demonstrated using an improved configuration with a broadband fiber Bragg grating and a piece of photonic crystal fiber. The laser generates more than 55 lines of optical comb with a line spacing of approximately 0.09 nm in a 1,565-5 nm region using pump powers of 3 dBm and 150 mW for the Brillouin and 980-nm pumps, respectively. The Brillouin erbium fiber laser with a fiber Bragg grating's reflectivity of 50% obtained a higher number of comb lines compared to that of 99% reflectivity.

Dispersion compensation technologies for femtosecond fiber system

Developed highly chirped broadband fiber Bragg gratings and suspended-core fibers are shown to offer flexible dispersion management and allow for femtosecond oscillators with transform-limited pulse quality. Such dispersion compensators could have potential, particularly for all-fiber chirped-pulse amplification systems.

基于光子晶体光纤的多波长布里渊双通放大激光器

A simple technique for achieving a stable, room temperature and multi-wavelength lasing with narrow linewidth is demonstrated using Brillouin fiber laser (BFL) with a 100-m-long photonic crystal fiber (PCF) in conjunction with a dual-pass configuration. A broadband fiber Bragg grating (FBG) operating in the C-band region is incorporated at the end side of the setup to allow a dual-pass operation. The proposed BFL can operate at any wavelength depending on the Brillouin pump wavelength and the FBG's reflection region used. With a Brillouin pump (BP) of 15.7 dBm, approximately 7 Stokes and 4 anti-Stokes lines are obtained with a line spacing of 0.08 nm.

High output power Erbium-Ytterbium doped cladding pumped fiber amplifier

The performance of a high output power Erbium-Ytterbium doped fiber amplifier (EYDFA) pumped by a 927 nm laser diode are proposed and experimentally investigated. The EYDFA provides a flat gain and output power higher than 23 dBm in the wavelength region from 1545 to 1566 nm using a double-pass configuration. A broadband fiber Bragg grating is used in the double-pass EYDFA to allow a double-propagation of the test signal in the gain medium and thus improves the gain and output power characteristics of the amplifier. The maximum output power of 390 mW is obtained at the maximum 927 nm pump power of 4.1 W which translates to a power conversion efficiency of about 10%.

FWM-based multi-wavelength erbium-doped fiber laser using Bi-EDF

We experimentally demonstrate a simple structure but efficient multi-wavelength erbium-doped fiber laser (EDFL) using a 49 cm Bismuth-based erbium-doped fiber (Bi-EDF) as gain medium. The Bi-EDF provides erbium amplification and FWM effect in the cavity to generate a stable multi-wavelength comb operating in C-band region. We have achieved more than 5 lines with peak power of more than −35 dBm and channel spacing of 0.5 nm by incorporating a broadband fiber Bragg grating and polarization controller in the ring cavity.

Effects of Pumping Scheme and Double-Propagation on the Performance of ASE Source using Dual-Stage Bismuth-Based Erbium-Doped Fiber

In this paper, a new configuration of the wide-band amplified spontaneous emission (ASE) source is proposed using dual-stage scheme with a broadband fiber Bragg grating. The ASE source utilizes a Bismuth-based erbium-doped fiber (Bi-EDF) as a gain medium with either forward or backward pumping scheme. A wide-band and flat ASE output is achieved using a forward pumping scheme with the power ripples of less than 4.9 dB and 3 dB bandwidth of 90.5 nm. The ASE spectrum obtained covers the whole C-, L- and extended L-band regions from 1520 to 1620 nm. However, the backward pumping scheme provides a better pumping efficiency as compared to the forward pumping. The total ASE power reaches up to 26.6 mW at maximum pump power of 320 mW with a pumping efficiency of 8%.

Wide-Band Bismuth-Based Erbium-Doped Fiber Amplifier With a Flat-Gain Characteristic

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, a bismuth-based erbium-doped fiber amplifier (Bi-EDFA) that operates in both the C- and L-band wavelength regions is demonstrated. The system employs two pieces of bismuth-based erbium-doped fiber (Bi-EDF) as the gain medium with a midway broadband fiber Bragg grating (FBG). The FBG functions to prevent the gain saturation at the C-band region, flatten the overall gain spectrum, and reduce the noise figure, particularly for the C-band. At an input signal power of <formula formulatype="inline"><tex Notation="TeX">$-$</tex></formula>30 dBm and a pump power of 150 mW for both pumps, a flat gain of around 29 dB is obtained with a gain variation of <formula formulatype="inline"><tex Notation="TeX"> $\pm$</tex></formula>3.5 dB within the wavelength region from 1525 to 1615 nm using a backward-pumping scheme. At an input power of 0 dBm, the gain varies from 10 to 13 dB within the wavelength range from 1530 to 1620 nm, while the corresponding noise figure varies from 9.5 to 14 dB over this wavelength range. </para>

Gain improvement in a dual-stage S-band EDFA by filtration of forward C-band ASE

Gain improvement in a dual-stage S-band erbium-doped fiber amplifier (S-band EDFA) is demonstrated using a broadband fiber Bragg grating (FBG) operating in the conventional-band (C-band) region or a C-band/S-band wavelength division multiplexing (WDM) coupler which filters out the forward C-band amplified spontaneous emission (ASE) in the amplifier system, thus increasing the population inversion in the S-band region. The gain for the amplifier with the WDM coupler increases by about 8.5 dB with an input signal power of −40 dBm, compared to that of the conventional dual-stage amplifier. The gain improvement varies from 4.0–9.2 dB at a wavelength region between 1480 to 1512 nm without a significant noise figure penalty.

Development and laboratory validation of in-line multiplexed low-coherence interferometric sensors

In this paper, we present the development and laboratory validation of in-line multiplexing for a low-coherence interferometric strain sensor suitable for industrial deployment and application to civil structures. The sensor is the multiplexed version of the standard SOFO, developed, produced and commercialized by Smartec SA. While the standard SOFO employs total reflectors at the end of the measurement and reference fibers, allowing measurement of the strain only over a single field, in the solution presented in-line multiplexing is obtained separating each measurement field by partial reflectors, consisting of broadband Fiber Bragg Gratings (FBGs) with a 5% reflectivity. Laboratory tests have been carried out on a prototype 3-field sensor, to investigate effectiveness, resolution and temperature sensitivity. Outcomes show a linear response of the sensor with RMS resolution lower than 3 μm, independent of the measurement base, of the same order as the single field sensor. Consistently with the theoretical prediction, the system exhibits an apparent thermal expansion coefficient of 2 μ ε °C −1, relatively low if compared with the thermal expansion coefficient of steel or concrete structures. This temperature dependency can even be eliminated by appropriate selection of the length of the reference fiber. Theoretical analysis indicates that the maximum number of fields that can be arranged in series is in the order of 10; however this limit can be overcome by appropriately selecting the power of the light source of the interrogation unit.

Experimental comparison of all-optical methods of chromatic dispersion compensation in long haul transmission at speeds of 10 Gbit/s

Feature Issue on Transmission in Optically Transparent Core NetworksDifferent techniques and scenarios of all-optical chromatic are compared experimentally. Chromatic dispersion was compensated both conventionally by dispersion compensating fibers and unconventionally using both channelized and broadband fiber Bragg gratings and Gires-Tournois etalons. Results are compared experimentally at a transmission speed of 10 Gbit/s. Emphasis was also given to tunability and broadband characteristics of elements.

Highly Efficient and High-Power Raman Fiber Laser Based on Broadband Chirped Fiber Bragg Gratings

A highly efficient and high-power Raman fiber laser was developed based on the use of broadband fiber Bragg gratings (FBGs) as optical couplers. The broadening of the Stokes signal is analyzed in both cases where the laser emission is restricted or not by the FBGs bandwidth. The use of broadband FBGs with minimized cladding-mode losses allows us to overcome the problem of power leakage outside the laser cavity through the input coupler. It is shown that by carefully tailoring the intracavity spectral losses and the FBGs losses, lasing efficiencies approaching the quantum limit can be obtained. In fact, 7.8 W of Stokes power with a conversion efficiency of 93.6% has been obtained

Gain and noise figure improvements in double-pass S-band EDFA

Double-pass short-wavelength band erbium-doped fiber amplifier (S-band EDFA) with enhanced gain and noise figure characteristics is demonstrated. It uses a broadband fiber Bragg grating (FBG) operating in conventional-band (C-band) region to reduce the C-band amplified spontaneous emission (ASE) in the amplifier system and thus increases the population inversion in the S-band region. The small signal gain is increased by about 2.7 dB for 1500 nm signal at pump power of 103 mW, compared with that of the conventional double-pass amplifier without the FBG. The corresponding noise figure is also improved by 0.5 dB.

Broadband fiber Bragg gratings for dispersion management

This paper provides an overview and technology update of a dispersion management component made from chirped fiber Bragg gratings. The history and technology of fiber Bragg gratings (FBGs) have been extensively covered in several excellent review articles, [1-6] book chapters, [7] and books. [8,9] We give a brief overview of fiber Bragg grating technology in this section and then focus on the details concerned with construction and performance of dispersion management devices in optical communications systems with a single broadband long-length grating used in reflection. Sampled chirped grating are sometimes referred to as broadband devices, but they actually have a narrow bandwidth of operation that is periodically repeated across a given spectral range. Although these periodic devices have shown promise as dispersion management devices in communications systems, they will not be discussed in this paper.