Fiber Brillouin Amplifier Research Articles

Characterization of Brillouin fiber generator and amplifier for optimized working condition of distributed sensors

The Brillouin fiber amplifier (BFA) has been used in Brillouin optical time and frequency domain analyzer based sensors. For BFA based distributed sensor the optimized working condition is to have the highest Brillouin gain, i.e., highest SNR, which avoids high pump depletion induced gain saturation. We have found that the optimum working condition for distributed sensor system is associated with the stimulated Brillouin scattering (SBS) threshold for BFA, which can be experimentally determined with Stokes power inflexion and/or Stokes spectrum linewidth minimum methods. This threshold depends on both pump and probe power instead of just the pump power as in Brillouin fiber generator (BFG), as well as on sensing length as confirmed by our experimental results and theoretical simulation. This was achieved by introducing the concept of absorption coefficient of the sensing medium defined as the ratio of the total output power to the total input power. We find that the medium absorption is minimized when input Stokes power is an order of magnitude lower than BFA threshold. This minimum is a signature of the balance between maximum Stokes gain and pump depletion which is also the reason why Stokes spectrum linewidth goes through a minimum.

在背向泵浦分布式光纤拉曼放大器中受激布里渊散射和瑞利散射的放大效应

The amplification effect on stimulated Brillouin scattering (SBS) and Rayleigh scattering in the backward pumped G652 fiber Raman amplifier (FRA) is studied. The pump source is a 1427.2-nm fiber Raman laser whose power is tunable between 0-1200 mW, and the signal source is a tunable narrow spectral bandwidth (l10 MHz) external cavity laser (ECL). The Rayleigh scattering lines are amplified by the FRA and Stokes SBS lines are amplified by the FRA and the fiber Brillouin amplifier. The total gain of SBS lines is the production of the gain of Raman amplifier and that of Brillouin amplifier. In experiment, the SBS gain is about 42 dB and the saturation gain of 25-km G652 backward FRA is about 25 dB, so the gain of fiber Brillouin amplifier is about 17 dB.

High-Power Low-Noise Fiber Brillouin Amplifier for Tunable Slow-Light Delay Buffer

A high-power low-noise fiber Brillouin amplifier (FBA) has been demonstrated for slow-light delay buffer. Its features including gain, gain saturation, and noise figure (NF), have been characterized. Among them, the gain saturation is highlighted because it is a fundamental limitation for FBA-based slow-light buffer. It is testified that the gain saturation is more easily achieved for lower signal-to-pump ratio (SPR), and the NF is reduced at higher pump level when below Brillouin threshold. The experiment demonstrated that up to 20-ns delay enhancement could be obtained in this high-power FBA for a -30-dBm input signal, as well as with low NF. Besides, the analysis on how the performance of the high power FBA affects the slow-light delay buffer has been presented.

Stimulated Brillouin Scattering in a Single-Mode Tellurite Fiber for Amplification, Lasing, and Slow Light Generation

In this paper, Brillouin gain performances of tellurite fiber are investigated for photonics applications. We demonstrate stimulated Brillouin amplification and lasing and the simulated performance of slow light generation in a single-mode tellurite fiber. A Brillouin gain of 29 dB is achieved in a 100-m tellurite fiber with a pump power of 10 mW at 1550 nm. A peak value of Brillouin gain coefficients of 1.6989 X 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-10</sup> m/W is measured on the base of gain characteristics. An all-fiber Brillouin laser with the maximum unsaturated power of 54.6 mW at 1550 nm and a slope efficiency of 38.2% is achieved from a 200-m tellurite fiber by employing a ring cavity. Furthermore, widely tunable (~27 nm) Brillouin comb laser with 26 lines spaced at 7.97 GHz is obtained from the ring laser cavity including an erbium-doped fiber amplifier (EDFA). A simple theoretical model based on laser threshold theory successfully explains the properties of Brillouin comb lasers. Stimulated Brillouin scattering (SBS)-induced time delay per unit power and per unit length is also calculated using the measured data of Brillouin gain coefficients. A peak value of 0.09246 ns/mW/m and a time delay slope efficiency of 1.75 ns/dB are obtained for this tellurite fiber. Potential performance of a tellurite fiber for slow light generation is clarified on the base of Brillouin gain characteristic. Our results show that tellurite fiber is a promising gain medium for Brillouin fiber amplifiers, lasers, and slow light generation due to its low background loss and large Brillouin gain coefficient.

Power Thresholds and Pump Depletion in Brillouin Fiber Amplifiers

The Brillouin fiber amplifier (BFA) has been used in Brillouin optical time (frequency) domain analyzer based sensors. The performance of this sensor depends on pump depletion which occurs when the threshold is reached and when the Brillouin gain is saturated. Although threshold definitions are common for Brillouin fiber generators (BFG), there is no explicit threshold definition for BFA. More importantly we find the maximum gain point corresponds to the optimized distributed sensing system where the depletion effect remains small to moderate. We find that only the method based on the determination of the power for which the pump becomes depleted, and hence, the Stokes gain saturated (i.e. inflexion method), remains valid for BFA. We also derive an analytical relation accounting for the various sensor key parameters such as fiber type and length as well as input Stokes power. The thresholds obtained with the analytical relation are within 10% of experimental and numerical values, which is maximum power that can be launched for a given optimum sensing configuration.

A New Frequency Model for Pump-to-Signal RIN Transfer in Brillouin Fiber Amplifiers

In this letter, we propose a novel frequency model to evaluate the pump-to-signal relative intensity noise (RIN) transfer in stimulated Brillouin scattering (SBS). For the first time, the RIN transfer in Brillouin fiber amplifiers has been numerically determined in the pump depletion regime both in the time and frequency domains. Moreover, an analytical expression of RIN transfer has been derived from the well-known SBS coupling equations when pump depletion is ignored. Experimental results are found to be in good agreement with the theoretical analysis.

Mathematical model of optical amplifier using nonlinear stimulated Brillouin scattering (SBS) in optical fiber

We demonstrate the results of a mathematical model for investigation the nonlinear Stimulated Brillouin Scattering (SBS), which can be employed to achieve high optical amplifier. The SBS is created by interaction between the incident We demonstrate the results of a mathematical model for investigation the nonlinear Stimulated Brillouin Scattering (SBS), which can be employed to achieve high optical amplifier. The SBS is created by interaction between the incident light and the acoustic vibration fiber. The design criteria and the amplification characteristic of the Brillouin amplifier is demonstrated and discussed for fiber Brillouin amplifier using different pump power with different fiber length. The results show, high Brillouin gain can be achieved with high pump power and long effective fiber length.and the acoustic vibration fiber. The design criteria and the amplification characteristic of the Brillouin amplifier is demonstrated and discussed for fiber Brillouin amplifier using different pump power with different fiber length. The results show, high Brillouin gain can be achieved with high pump power and long effective fiber length.

Storage capacity of slow-light tunable optical buffers based on fiber Brillouin amplifiers for real signal bit streams

We present a theoretical analysis of the slow-light tunable optical buffers based on fiber Brillouin amplifiers (FBA). Its storage capacity was discussed for return-to-zero (RZ) and non-return-to-zero (NRZ) bit streams. Gain saturation and pulse broadening are two key factors which limit the buffer capacity. Gain saturation is an inherent characteristic of the FBA. Broadening of the amplified pulse always accumulates with increasing gain owing to the dispersion during stimulated Brillouin scattering (SBS) process. It is shown that the maximum buffer capacity varies with data bit rate and for continuous wave (CW) or quasi-CW pump it is 0.53 and 1.04 bit for RZ and NRZ respectively. Also, the optimum data bit rate to achieve the best storage capacity is obtained.

High-gain Brillouin amplification: an analytical approach

We derive a closed-form approximate analytical formula for the gain of a Brillouin fiber amplifier operating in the depleted pump regime. We take into account the material loss of the medium, which is a strong effect in optical fibers. We validate obtained results numerically and experimentally. The presented analysis can be used to accurately predict the performance of high-gain Brillouin fiber amplifiers.

Threshold level and gain of forward stimulated Brillouin scattering in a forward pumped s-band discrete DCF fibers Raman amplifier

Amplification effect of forward stimulated Brillouin scattering (SBS) lines on the forward pumped s-band discrete DCF fiber Raman amplifier (FRA) has been studied. Pump threshold power of the forward first order Stokes SBS (FSB1-), second order Stokes SBS (FSB2-) and third order SBS (FSB3-) in the forward pumped FRA are 1.5 mW, 1.4 mW and 1.7 mW, respectively. The Stokes SBS lines are amplified by FRA and fiber Brillouin amplifier (FBA) at the same time. Gain of amplification is given as GA=GR · GB, where GR is Raman gain and GB is Brillouin gain. Saturation gain of FSB1-, FSB2- and FSB3- are about 52 dB, 65 dB and 65 dB, respectively. The saturation Raman gain of 10 km DCF forward FRA is about 14 dB, so Brillouin gain of FSB1-, FSB2- and FSB3- are about 38 dB, 51 dB and 51 dB, respectively. The forward cascaded SBS lines have been observed.

Numerical study of all-optical slow-light delays via stimulated Brillouin scattering in an optical fiber

We study numerically all-optical slow-light delays in room-temperature single-mode optical fibers induced by stimulated Brillouin scattering. We consider the propagation of a pulse through a cw-pumped Brillouin fiber amplifier, where the carrier frequency of the pulse is tuned near the Stokes resonance. Pulse delay and broadening of the Stokes pulse are studied in the small-signal and gain-saturation regimes. Pulse delay is shown to be limited by saturation of the Brillouin amplifier. In the small-signal regime, both time delay and pulse broadening increase with increasing gain. In the gain-saturation regime, both time delay and broadening decrease with increasing gain, and the pulse even achieves advancement. Time delay of more than one pulse-width is observed with modest pulse distortion, and over one pulse-width advancement can be obtained with larger pulse distortion in the gain-saturation regime.

Origin of spectral hole burning in Brillouin fiber amplifiers and generators

We show theoretically that the spectral hole burning recently observed in Brillouin fiber amplifiers and generators can be interpreted without invoking an inhomogeneous broadening of the Brillouin line. By using the three-wave model of stimulated Brillouin scattering (SBS), we first investigate the linear response of a Brillouin fiber amplifier to a weak amplitude modulation of the injected signal wave. The transfer functions that fully characterize this response are analytically calculated. The fact that they may exhibit a dip is shown to be due both to the gain saturation and to the coupling between the pump and signal perturbations that counterpropagate around the steady-state intensity profiles. These transfer functions also appropriately characterize the way through which noisy perturbations are filtered in SBS fiber generators. The spectral hole burning observed in generators is thus simply connected to spectral hole burning studied in SBS amplifiers.

Spectral gain hole burning and modulation instability in a Brillouin fiber amplifier

We investigate theoretically the gain spectrum of a Brillouin fiber amplifier in the saturated region. When the amplifier is operated in the saturated region a hole is burned in the single-pass Brillouin gain spectrum, and peaks appear at frequencies determined mainly from the round-trip time of the amplifier, causing modulation instability in the amplified signal. This type of modulation instability originates intrinsically from signal amplification by the counterpropagating pump beam, which is depleted by the strong signal beam.

A coherent approach to stationary stimulated Brillouin fiber amplifiers

An analytical stationary solution is proposed for the collinear Brillouin fiber mirror in the frame of the 1-D-coherent 3-wave model, in which decoupled phases allow side-resonance interaction, the conservation of the impulsion being insured by a nonlinear phase gradient. The Lorentzian shape of the gain curve of low efficiency stationary SBS amplifiers is then justified, even when the interaction is strong enough to stimulate an acoustic wave with a narrow spectral width. It is shown that, when SBS efficiency increases, the gain curve first exhibits some gain narrowing, then saturates, yielding for high pump powers a spectral band larger than the spontaneous Brillouin bandwidth.

A supervisory channel scheme for EDFA transmission systems that uses Brillouin amplification

A supervisory (SV) signal transmission channel scheme that makes use of fiber Brillouin amplification is proposed for Er-doped fiber amplifier (EDFA) transmission systems. In the scheme, the forward line signal pumps the backward SV signal through Brillouin amplification. The scheme is realized by combining a new type of EDFA repeater based on circulators and an optical frequency scanning technique that ensures the SV signal frequency falls within the narrow Brillouin gain band. Bidirectional transmission over a 130 km transmission line is confirmed by successfully measuring the bit error rates of the 2.4 Gb/s line signal and the 5 kb/s SV signal.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Characteristics of a semiconductor laser pumped brillouin amplifier with electronically controlled bandwidth

We demonstrate the operation of a semiconductor laser pumped fiber Brillouin amplifier. An optical gain of 5.5 dB/mW of pump power is obtained. The 15-MHz intrinsic bandwidth of the amplifier was extended more than one order of magnitude by adding frequency modulation to the pump laser. Bit-error-rate receiver sensitivity measurements with an in-line Brillouin amplifier demonstrate a 16-dB improvement in the system gain at 10 Mbit/s and a 8.5-dB improvement at 90 Mbit/s. Noise calculations show that the amplifier has an excess noise factor of 50-500 depending on the amplifier length and pump power.