Brillouin Gain Medium Research Articles

A 75 GHz Brillouin Stokes Channels For High Data Rate DWDM Communication Systems

The experimental results of a 75 GHz Brillouin Stokes channels are demonstrated in this paper. Three dispersion compensation fiber (DCF) spools and one single mode fiber (SMF) spool are used as a Brillouin gain medium. An erbium doped fiber amplifier (EDFA) sections are used to amplify the generated Stokes channels and to reduce the Brillouin Stokes threshold inside the cavities. Laser pump of 1480 nm with total power of 470 mW are used for the EDFA sections as a pump power unit. In our proposed setup, four channels with 75 GHz spacing, high Stokes power of about 10 mW, and large optical signal to noise ratio (OSNR) of about 52 dB are achieved at Brillouin pump power of 25 mW. The achieved channels are tuned over 15 nm from 1565 to 1580 nm. within the entire tuning range up to 25 Stokes channels with 75 GHz spacing can be utilized. High data rate of about 800 Gb/s can be obtained per single channel at this wide channel spacing. Therefore, the total data rate that could be achieved within the obtained tuning range is about 20 Tb/s.

Stabilized single-frequency sub-kHz linewidth Brillouin fiber laser cavity operating at 1 µm.

We experimentally demonstrate a stabilized single-frequency Brillouin fiber laser operating at 1.06µm by means of a passive highly nonlinear fiber (HNLF) ring cavity combined with a phase-locking loop scheme. The stimulated Brillouin scattering efficiency is first investigated in distinct single-mode germanosilicate core fibers with increasing G e O 2 content. The most suitable fiber, namely, 21mol.% G e O 2 core fiber, is used as the Brillouin gain medium in the laser cavity made with a 15-m-long segment. A Stokes lasing threshold of 140mW is reported. We also show significant linewidth narrowing (below 1kHz) as well as frequency noise reduction compared to that of the initial pump in our mode-hop free Brillouin fiber laser.

Analytical investigation of GeO2-doped optical fibers to build Brillouin lasers at 1300 nm

The 1.5 µm spectral region concentrates the most substantial attention on building fiber laser sources for communications applications. However, data transmission in this spectral region is quite congested, requiring exploring new neighboring regions. In particular, 1.3 µm, usually defined as the zero-dispersion band, currently constitutes an active field of research, and the development of fiber laser sources in this wavelength band is of substantial interest to expand the capabilities of existing photonic operations. Previous experimental investigations have already shown that the peak stimulated Brillouin scattering efficiency is strongly affected by the concentration of GeO2 doping in single-mode fibers. In this context, this work presents an analytical investigation of the performance of a Brillouin fiber laser at 1.3 µm using optical fibers doped with different GeO2 concentrations as a Brillouin gain medium. The results obtained suggest that optical fibers doped with high GeO2 concentrations can be a simple and effective solution to build Brillouin lasers with better efficiency in the 1.3 µm band employing shorter fiber lengths with low pump power values.

Tunable 60 GHz Multiwavelength Brillouin Erbium Fiber Laser

An experimental study of a tunable 60 GHz multiwavelength Brillouin erbium fiber laser is presented in this paper. Two unidirectional ring laser cavities and two pre-amplification laser cavities are used. In the first three cavities, a Brillouin gain medium is presented with a dispersion compensation fiber (DCF) spool, and a single-mode fiber (SMF) spool is used as a Brillouin gain medium in the fourth cavity. Three erbium amplifiers are utilized to supply enough gain to the generated Brillouin Stokes signal and to suppress cavity losses. For these three amplifiers, up to 450 mW (150 mW for each) of a 1480 nm pump power is used. In our proposed configuration, four sextuple Brillouin Stokes signals with a high power of 10 dBm and more than 55 dB as an optical signal-to-noise ratio are achieved. The obtained Brillouin Stokes signals can be tuned over 30 nm (1560–1590 nm) and can be easily used in dense wavelength division multiplexing in optics communication systems.

Compact Brillouin comb laser in Chalcogenide fiber assisted by four-wave mixing

We experimentally demonstrate a multiwavelength Brillouin comb generation employing a segment of As2S3 chalcogenide fiber as the Brillouin gain medium. The extremely high nonlinear and Brillouin gain coefficients allow the As2S3 fiber length to be as short as 4.2 m. A compact Brillouin comb laser composed of multiple Brillouin Stokes and anti-Stokes channels is generated from the As2S3 fiber either with or without ring cavity feedback through the interaction of stimulated Brillouin scattering and four-wave mixing effects. Different output couplings are used to extract the Brillouin comb laser when the cavity feedback is connected. A high laser power of 927 mW and multiple laser channels of 20 are achieved with an output coupling of 90 % and 10 %, respectively. A trade-off between the power threshold, laser channel number, output power and slope efficiency should be considered when optimizing the optical performance of the multiwavelength Brillouin laser.

Enhanced stimulated Brillouin scattering utilizing Raman conversion in diamond

Cascaded Brillouin lasers based on guided-wave structures are applied across a range of important fields such as optical communications, microwave photonics, and sensing. However, restricted by the volume and available transmission range of the gain medium, the power output and wavelength diversity of guided-wave Brillouin devices are somewhat limited. In this work, we report the design and development of a cascaded Brillouin laser based utilizing a free-space optical layout with a diamond crystal as the Brillouin gain medium. A quasi-continuous-wave, 1 μm laser was used as the pump laser, and Raman wavelength conversion is used as an intermediate process to facilitate stimulated Brillouin scattering with a low threshold. When the output transmission of the diamond cavity is 0.37% and the incident pump power is 220 W, cascading of the Brillouin–Stokes field to the eighth Stokes and the seventh anti-Stokes orders was observed. By adjusting the cavity length, the order of the cascaded Brillouin laser output is controlled. A comprehensive analysis of the Brillouin generation process and the cascade of Stokes orders is undertaken for different incident pump powers and cavity lengths. This work is expected to enable practical applications of high-power Brillouin lasers and Brillouin frequency combs.

Numerical analysis of the pump’s spectral linewidth impact on single and multi-wavelength Brillouin fiber lasers

Brillouin fiber lasers (BFLs) are a promising optical source technology for industrial and academic purposes that have experienced continuous progress in recent years. Currently, part of this development is focused on delivering laser solutions with low resonator loss, relatively low pump threshold, high efficiency, very small linewidth, and multi-wavelength architecture. In this perspective, this study employs an accurate numerical model based on an analytical solution to investigate the effect of the pump’s spectral linewidth on BFLs working both in single and cascaded multi-wavelength configurations. Output powers, thresholds, and the Stokes lines number simulated are analyzed here using a standard single-mode optical fiber as the Brillouin gain medium. The numerical results obtained not only allow identifying the regions of the pump’s spectral linewidth in which there is greater, moderate, or even no suppression of the stimulated Brillouin scattering inside the laser cavity but also provides a deep understanding of the internal dynamics of the BFLs cavities.

Multiwavelength Brillouin Generation in Bismuth-Doped Fiber Laser With Single- and Double-Frequency Spacing

Multiwavelength fiber lasers operating in the 1.3 μm wavelength region are of great interest as they complement existing systems in the conventional optical communication band of 1.55 μm. In this work, a multiwavelength Brillouin fiber laser with single- and double-Brillouin frequency spacings operating in 1.3 μm is proposed and demonstrated using a dispersion compensating fiber (DCF) as the Brillouin gain medium. A bismuth-doped fiber serves as the laser gain medium. At the maximum pump power of 1021 mW and with the Brillouin pump set at 11 dBm, up to 7 Brillouin Stokes lines with a wavelength spacing of 0.074 nm are obtained in the single-spaced configuration. In the case of the double-spaced configuration, 14 Stokes lines are generated with a wavelength spacing of 0.15 nm between the even Stokes lines. By tuning the central wavelength of the Brillouin pump, both laser configurations are wavelength-tunable with a range of 93 nm and 19 nm for the single-spaced and double-spaced Brillouin lasers respectively. This is, to the best of the author's knowledge, the first demonstration of a multiwavelength/Brillouin laser using a bismuth-doped fiber as the laser gain medium.

Simulation solution for single and cascaded multi-wavelength Brillouin fiber lasers based on an analytical model

Abstract Here we propose a simulation model based on a previously reported analytical description of the Brillouin gain, that takes into account pump depletion, which allows us to make very accurate calculations for Brillouin fiber lasers (BFLs) working both in a single and cascaded multi-wavelength configurations. Output powers and conversion efficiencies are analyzed and compared with experimental results for various lasers setups using 25 km of a non-zero dispersion-shifted fiber (NZDSF) as the Brillouin gain media. In our experimental investigations, we used a pump laser at 1565 nm, with a bandwidth of 1 kHz, and output powers varying from 0 to its maximum value of 14 mW. We analyzed the laser behavior under various conditions using output couplers with output ratios varying from 10% to 90%, and to generate the cascaded Brillouin laser we have used a 10 m Erbium-doped optical fiber amplifier as a gain block in a separated cavity. Additionally, a spectral reconstruction is made based on power predictions of our model for the cascaded BFL with excellent agreement with experimental data.

Managing Brillouin frequency spacing for temperature measurement with Brillouin fiber laser sensor

Managing Brillouin frequency spacing for temperature measurement with Brillouin fiber laser sensor is proposed and demonstrated. By managing Stokes light wave resonance of different orders, Brillouin lasers with different Brillouin frequency spacing are obtained. In the absence of EDFA, using an optical coupler with 5 km SMF, only the 1st-order (S1) with single frequency shift circulates in the ring. Using a three-port optical circulator with 5 km SMF and adding EDFA, only the 2nd-order (S2) with double frequency shift is in the ring. When the three-port circulator is replaced with a four-port, fiber under test 1 (FUT1) with 10 km SMF and FUT2 with 5 km SMF are used as Brillouin gain medium and generate the 3rd-order Stokes (S3) with triple frequency shift. Temperature is measured directly by beat frequencies between the pump and the 1st-order, 2nd-order, 3rd-order Stokes. About 1.036 MHz/°C, 2.006 MHz/°C and 3.104 MHz/°C sensitivity are consistent with the theoretical value and ± 0.05 dB power fluctuation and 0.2 °C temperature stability keep the same with the previously reported results. It is expected to be widely used in the field of fiber optic sensing.

Widely triple Brillouin frequency shift multiwavelength Brillouin erbium fiber laser

We experimentally propose simple and widely tunable multiwavelength Brillouin erbium fiber laser with triple Brillouin frequency spacing. Only two dispersion compensation fiber spools with total length of 12 km, as a Brillouin gain media and erbium-doped fiber amplifier section with maximum pump power of 220 mW are utilized. In the developed structure, we achieved six triple Stokes lines with high peak power and large optical signal to noise ratio of more than 45 dB. Wide tuning range of 50 nm (1530–1580 nm) in the absence of self lasing cavity modes is recorded using both of high Brillouin pump and extracting the residual pump power outside the cavity.

Tunable 50 GHz laser comb generation of multiwavelength Brillouin erbium fiber laser

We experimentally proposed widely tunable multiwavelength Brillouin erbium fiber laser with quintuple Brillouin frequency spacing (∼ 0.4 nm, ∼ 50 GHz). Only three dispersion compensation fiber spools with total length of 15 km as a Brillouin gain media are used. Two sections of an erbium-doped fiber amplifier with maximum pump power of 220 mW are utilized. In the developed structure, at port1, we achieved four quintuple Stokes lines of about 10 dB peak power and large optical signal to noise ratio of more than 50 dB. Wide tuning range of 40 nm (1540–1580 nm) in the absence of free running modes is recorded using high BP power, BP pre-amplification, and extracting the residual pump power outside the cavity. In addition, another 14 quintuple Stokes channels are produced at another four output ports (port 2 to port 5). The whole generated 50 GHz wavelength spacing signals can be used in dense wavelength division multiplexing communication systems as such large channel spacing can be easily recognized by the optical detector at the receiver terminal.

Triple Brillouin frequency spacing Brillouin fiber laser sensor for temperature measurement

• A triple Brillouin frequency spacing Brillouin fiber laser sensor for temperature measurement is proposed and demonstrated. • Triple Brillouin frequency spacing Brillouin is used as a point temperature sensor. • Fiber under test 1 (FUT1) with 10 km SMF and FUT2 with 5 km SMF are used as Brillouin gain medium and generate the 1st-order Stokes (S1) and 3rd-order Stokes (S3) and 2nd-order Stokes (S2) respectively. • Only the pump and S3 circulate in the ring with two optical circulators of three and four port. • About 3 MHz/°C sensitivity is consistent with the theoretical value and ±0.05 dB power fluctuation and 0.2 °C temperature stability are obtained. • The proposed structure makes it convenient for more applications. A triple Brillouin frequency spacing Brillouin fiber laser sensor for temperature measurement is proposed and demonstrated. Fiber under test 1 (FUT1) with 10 km SMF and FUT2 with 5 km SMF are used as Brillouin gain medium and generate the 1st-order Stokes (S1) and 3rd-order Stokes (S3) and 2nd-order Stokes (S2) respectively. Only the pump and S3 circulate in the ring with two optical circulators of three and four port. External perturbations can be effectively reduced and Brillouin gain bandwidth not is deteriorated with 10 MHz bandwidth. About 3 MHz/°C sensitivity is consistent with the theoretical value and ±0.05 dB power fluctuation and 0.2 °C temperature stability are obtained. The proposed structure makes it convenient for more applications.

Efficient Brillouin lasing and multi-Stokes generation at 2004 nm

We demonstrate efficient single- and multi-wavelength lasers at 2 μm exploiting Brillouin scattering in a SM1950 fiber. Using a SM1950 fiber as the Brillouin gain medium, higher output Stokes power and slope efficiency are achieved for a threshold pump power that is three to four times lower than the Brillouin lasing threshold in a longer length SMF with similar or higher feedback factors. We realize single and multi-Stokes Brillouin lasers with low threshold pump powers of ∼ 130 mW and ∼ 385 mW, respectively, using a 100 m SM1950 fiber ring and a Fabry-Perot resonator. For a fixed SM1950 cavity length, as the feedback factor is varied from 90% to 50%, the output Stokes power and slope efficiency increased four times with only a small penalty on lasing threshold. For multi-Stokes Brillouin lasing, we observe 14 lines, including four-wave mixing components, at a maximum pump power of 822 mW. To the best of our knowledge, this is the first detailed study of Brillouin lasing at 2 μm that studies the effect of different cavity parameters such as length, feedback factor, and resonator geometry on Brillouin lasing.

Dual-wavelength Brillouin-erbium fiber laser with tunable wavelength spacing

Abstract A novel wavelength-spacing tunable dual-wavelength Brillouin-erbium fiber laser is proposed and demonstrated experimentally. The dual-wavelength lasing is achieved by combining the erbium-doped fiber laser (EDFL) and the first-order Brillouin laser using a 4 m high nonlinear fiber (HNLF) as Brillouin gain medium. The evolutionary power spectrum of the EDFL and the first-order Brillouin laser are investigated through adjusting the output power of tunable laser source (TLS) and 980 nm pump. The high stability of the single-and dual-wavelength operation are experimentally verified by the measured wavelength variation of ≤0.01 nm and power fluctuation of ≤1.6 dB within 100 min. With the good tunability of the TLS, the wavelength spacing of a dual-wavelength operation could be achieved in the pass band of the FBG. The fiber laser will find potential applications in fiber sensing and microwave photonics areas.

Demonstration of forward cascaded Brillouin lasing using a silicon-based rectangular spiral microring resonator assisted by EDFA

We experimentally demonstrate the forward cascaded Brillouin lasing exploiting a silicon-based rectangular spiral microring resonator assisted by an erbium-doped fiber amplifier. To realize the enhanced Brillouin nonlinearity, the optical and acoustic fields are effectively confined by partly suspending the spiral resonator. The free spectral range is precisely designed to match the half of the Brillouin frequency shift to guarantee Brillouin laser oscillation. The fabricated spiral resonator is incorporated in a fiber loop to serve as not only a resonance-enhanced element to generate the internal pump lasing for Brillouin scattering but also a Brillouin gain medium to excite Brillouin lasing. The spiral structure allows a 0.6368 cm long resonator waveguide to be enclosed in a small footprint of 250 × 330 μm2. Four anti-Stokes and three Stokes lasing lines are obtained with the Brillouin frequency shift of about 12.0463 GHz. The proposed approach provides a potential way to implement Brillouin lasing on a silicon-based chip.

Multi-wavelength Praseodymium fiber laser using stimulated Brillouin scattering

A multi-wavelength Brillouin Praseodymium fiber laser (MWBPFL) operating at 1300 nm region is demonstrated based on the hybrid scheme by utilizing Brillouin gain medium and Praseodymium-doped fluoride fiber as linear gain medium. A 15 µm air gap is incorporated into the cavity to allow the switching of Brillouin frequency spacing from double to single spacing. Under the Brillouin pump of 8 dBm and the 1020 nm pump power of 567.2 mW, 36 Stokes lines with a wavelength spacing of 0.16 nm and 24 Stokes lines with a wavelength spacing of 0.08 nm are achieved. The wavelength tunability of 8 nm is realized for both MWBPFLs by shifting the Brillouin pump wavelength. The MWBPFLs exhibit an excellent stability in the number of generated Stokes and power level over one-hour period.

Cascaded superluminal propagation via Brillouin lasing resonance in optical fibers

All-optical group velocity manipulation of light, so-called slow and fast light, has drawn extensive attention due to its potential applications in the fields of optical signal processing, light storage, light-matter interaction enhancement, hypersensitive sensing and temporal cloak. Tremendous approaches of slow and fast light generation have been widely demonstrated by the creation of the sharp spectral resonances in the past decade. Specifically, superluminal propagation (larger-than-light velocity c ) through the optical media has been proposed and validated in anomalous dispersion media. One effective approach is employing stimulated Brillouin scattering to harness the narrowband spectral resonance and thus generate slow and fast light in the optical fiber. In particular, Brillouin lasing oscillation has been experimentally demonstrated to generate fast and superluminal propagation in ten-meter optical fibers. Afterwards, the propagating distance over hundreds of meters has been experimentally demonstrated by the suppression of multiple-longitudinal-mode operation. However, the delay-bandwidth product or the fractional advancement is still fundamentally limited in conventional fast and slow light system. For example, the maximum advancement as well as the fractional temporal advancement are practically restricted due to the Brillouin gain saturation and multiple longitudinal mode lasing operation under high pump power in the Brillouin lasing resonance-based fast and superluminal system. In this paper, we experimentally validate the extension of time advancement of superluminal propagation based on Brillouin lasing oscillation for the first time. By employing two stages of single-frequency Brillouin lasing fiber ring resonators, Stokes lasing resonance was effectively created in each fiber ring cavity to deliver Brillouin-induced loss resonance at the center frequency of pump, which essentially leads to fast light and superluminal propagation of the pump light. Consequently, Gaussian signal pulses with the pulse width of 500 ns experiences cascaded Brillouin-induced fast light and even negative group-velocity superluminal propagation. The temporal advancement was basically extended to 365.8 ns which is twice than that of single stage fast light and superluminal system. Correspondingly, the fractional advancement was increased from 0.36 to 0.73. The maximum group velocity was 6.3 times larger than the light speed c in vacuum while negative-group- velocity propagation can be found in the range of −9.9 to −0.2 by increasing the total input power from 593.2 to 812.0 mW. Furthermore, the group index can be manipulated in the range of 1.5 to −4.0 by simply varying the total input pump power. It indicates superluminal signals can be cascaded to essentially extend the propagation distance and enlarge the temporal advancement. The scheme exhibits robustness in cascading Brillouin spectral loss resonance for temporal advancement enhancement as well as propagating distance extension. More importantly, the cascading design could basically eliminate the fundamental limitation introduced by Brillouin gain saturation and multiple longitudinal lasing mode under high power operation in single stage Brillouin fast and superluminal system. Further optimization could also be implemented by utilizing the nonstandard specialty fibers as Brillouin gain medium to achieve an efficient Brillouin lasing resonance for an enhanced advancement efficiency. Additionally, the combination with the cascading technique and long-cavity single-frequency Brillouin lasing resonance could enable the feasibility of distance-limitless and large-advancement superluminal propagation, paving a way for promising applications in sensing and temporal cloak.

High-efficiency Brillouin random fiber laser using all-polarization maintaining ring cavity.

We report a high-efficiency (25%) Brillouin random fiber laser (BRFL) with Brillouin gain medium of 2-km polarization maintaining fiber (PMF) as well as distributed Rayleigh scattering feedback from 500-m PMF. The characteristics of lasing efficiency and relative intensity noise (RIN) have been comprehensively studied comparing with the BRFLs with half-open ring cavity and bidirectional pumping linear open configuration. The enhanced lasing efficiency using PMF-BRFL with half-open ring cavity enables sub-kHz linewidth, lower phase fluctuation and frequency jitter comparing with phase locked pump laser, thanks to the polarization-matched efficient Brillouin gain in PMFs. The RIN and frequency instability of the proposed PMF-BRFL induced from external disturbance, e.g., mechanical and thermal noise, have been effectively suppressed with respect to conventional SMF-based BRFL.

A tunable multi-wavelength Brillouin–erbium fiber laser with fourfold Brillouin frequency spacing

We have experimentally demonstrated a tunable multi-wavelength Brillouin–erbium fiber laser with over 40 GHz spacing utilizing two cascaded double Brillouin-frequency-spacing cavities. In this laser configuration, two segments of 25 km-long single-mode fibers are used as Brillouin gain medium in each ring cavity, and a segment of 8 m-long erbium-doped fiber with 980 nm pump is employed to amplify Brillouin pump (BP). At BP wavelength of 1550 nm, BP power of 8.3 dBm (6.8 mW) and the maximum 980 nm pump power of 27.78 dBm (600 mW), seven output channels with fourfold Brillouin-frequency spacing, and the tuning range of 15 nm from 1545 to 1560 nm are achieved. The proposed multi-wavelength Brillouin–erbium fiber laser has wide applications, such as in microwave signal generation and optical communications.