Distributed Raman Amplification Research Articles

High gain distributed Raman amplifier for orbital angular momentum mode-division multiplexing and wavelength-division multiplexing in a 104-km ring-core fiber over the C + L band

Mode-division multiplexing (MDM) and wavelength-division multiplexing (WDM) are regarded as effective solutions for enhancing the communication capacity of fiber-optic transmission systems. To extend the transmission distance, a suitable amplification technique is required to amplify the signal light, with distributed Raman amplifier (DRA) offering a high-flat gain. In this paper, we experimentally demonstrate the transmission of 3 orbital angular momentum (OAM) mode-division multiplexing and 9 wavelength-division multiplexing ranging from 1530 nm to 1610 nm over a 104-km self-designed ring-core fiber (RCF) with the assistance of DRA. The homemade all-fiber mode selective couplers (MSCs) can (de)multiplex OAM modes (OAM01, OAM11, OAM21) efficiently in long-distance MDM + WDM fiber-optic transmission systems. The OAM-DRA provides high gain (with an on-off gain greater than 10 dB) as well as flat gain (with a differential wavelength gain of less than 0.88 dB and a differential mode gain of less than 0.28 dB) over the C + L band.

Weak signal ultrafast interrogation of a micro-nano FBG probe sensor based on the hybrid amplified dispersion Fourier-transform method

To elucidate the thermal transport mechanisms at interfaces in micro- and nanoscale electronic devices, real-time monitoring of temperature variations at the microscopic and nanoscopic levels is crucial. Micro-nano fiber Bragg grating (FBG) sensors have been demonstrated as effective in-situ optical temperature probes for measuring local temperatures. Time-stretch dispersion Fourier transform (TS-DFT) that enables fast, continuous, single-shot measurements in optical sensing has been integrated with a micro-nano FBG probe (FBGP) for local temperature sensing. However, its temperature sensitivity and interrogation resolution are limited by the detection sensitivity. In this paper, we propose a hybrid amplified dispersion Fourier transform (ADFT) method to achieve ultrafast interrogation of FBGP’s weak signal. Thanks to the combined effect of TS-DFT and hybrid optical amplification, the reflection signal of the FBGP is amplified, and the wavelength shift of the FBGP sensor is converted to a temporal spacing change between two dispersed pulses through dispersion-induced wavelength-to-time mapping. The proposed method uses a homemade dissipative soliton mode-locked laser as the light source. The hybrid optical amplification technique comprises a L-band erbium-doped fiber amplifier and a distributed Raman amplifier. Their noise figure and net gain for the FBGP are 4.81 dB and 15.93 dB, respectively. In addition, the temperature calibration experiments show that a sampling rate of 51.43 MHz and the maximum temperature measurement error of 1.98°C are achieved within the temperature range of 20.3°C to 97°C. The stability of the net gain provided by the hybrid ADFT system is demonstrated by the coefficient of variation, which ranges from 2.22% to 2.95% in the peak voltage signal of the FBGP. This approach applies to scenarios requiring the handling of weak optical signals, particularly in temperature measurement at the micro-nano scale.

Correction of the GN Model for Fiber Optical Communication Links with Distributed Raman Amplification

Correction of the GN Model for Fiber Optical Communication Links with Distributed Raman Amplification

System Performance Analysis of Distributed Raman Amplification With Dual-Order Forward Pumping

System Performance Analysis of Distributed Raman Amplification With Dual-Order Forward Pumping

Total net-rate of 27.88 Tb/s full C-band transmission over 4,550 km using 150 km span length and high-gain EDFA amplification

We experimentally demonstrate a total net-rate of 27.88 Tb/s for C-band wavelength-division multiplexing (WDM) transmission over an ultralong span-length of 150 km. It is the largest net capacity × span-length product of 4182 Tb/s·km for C-band, single-core, standard single-mode optical fiber transmission over a length of more than 3,000 km. A total of 99 channels, spaced at 50 GHz intervals, are employed for transmitting 32 GBaud probabilistically constellation-shaped (PCS) 64QAM signals with an information entropy of 5.5. High gain amplifiers can achieve wavelength-division multiplexing (WDM) transmission with a bandwidth of 6.25 THz, at a noise figure below 4.3 dB, without the assistance of distributed Raman amplification.

Dense wavelength division multiplexing scheme based on effective distributed inline light fiber Raman amplifier configuration

Abstract This paper demonstrated the dense wavelength division multiplexing scheme based on effective distributed inline light fiber Raman amplifier configuration. Various forward/backward and bidirectional pumping power configurations are studied versus fiber reach. Output light signal power is demonstrated against fiber reach without Raman amplification technique. Output light signal power in the forward Raman amplification scheme is clarified with pumping power of both 500 mW and 700 mW in various fiber channel configurations. As well as output light signal power in the backward Raman amplification scheme with pumping power of both 500 mW and 700 mW in various fiber channel configurations. Amplification Raman gain parameter coefficient is demonstrated with various values of pumping power pump based on various fiber channel configurations. Backward amplification net parameter gain is studied for different single mode/true wave/freelight fibers channel configuration at different both pumping power values and fiber reach. As well as the forward amplification net parameter gain is clarified for different single mode/true wave/freelight fibers channel configuration at different both pumping power values and fiber reach.

Experimental comparison of E-band BDFA and Raman amplifier performance over 50 km G.652.D fiber using 30 GBaud DP-16-QAM and DP-64-QAM signals.

We compare the performance of three optical amplifiers in the E-band: a bismuth-doped fiber amplifier (BDFA), a distributed Raman amplifier, and a discrete Raman amplifier (RA). Data transmission performance of 30 GBaud DP-16-QAM and DP-64-QAM signals transmitted over 50 km of G.652.D fiber is compared in terms of achieved signal-to-noise (SNR). In this specific case of relatively short distance, single-span transmission, the BDFA outperforms the distributed and discrete Raman amplifiers due to the impact of fiber nonlinear penalties at high input signal powers.

Performance analysis of real-time multi-wavelength nonlinear DRA for the next-generation photonic network

A new disintegrated channelization approach for the backward pumped nonlinear distributed Raman amplifier is proposed by enacting the differential coupled equations of Raman amplification, in fiber, trailing by the solution of NLSE using the first integral method first time to the best of our knowledge. A nonlinear channel modeling-based simulation is adapted for the approximation of the Raman gain profile. To realize the real-time dynamic system, 16 multiplexed channels of prime C-band are employed in a QPSK/NRZ modulation environment with a 100 Gbps bit rate for optical network reconfiguration. A non-uniform gain is reported while the disparity in BER is observed from 10−12 to 10−8.

1.28 Tbps DWDM optical network design using a dispersion compensating distributed Raman amplifier over S-band

1.28 Tbps DWDM optical network design using a dispersion compensating distributed Raman amplifier over S-band

214.7 Tbit/s S, C, and L-band transmission over 50 km SSMF based on silicon photonic integrated transceivers

We experimentally demonstrate a 214.7 Tbit/s generalized mutual information (GMI) estimated throughput by ultra-wideband wavelength division multiplexing (WDM) transmission in standard single-mode fiber (SSMF). With 50-GHz grid, 396 transmission channels are used to deliver 49 GBaud probabilistically constellation-shaped (PCS) 256 quadrature amplitude modulation (QAM) and PCS-64QAM signals. Silicon photonic integrated transceiver is employed to complete electro-optic and optic-electro conversion of the modulated signals. S, C, and L-band rare-earth-doped amplifiers enable the 19.8 THz bandwidth WDM transmission without the assistance of distributed Raman amplification. The measured data rate shows great potential for Silicon photonic devices deployed in ultra-wideband WDM transmission.

Ultralow noise C + L wideband WDM-IMDD transmission at 18 × 112 Gbps by using hybrid second-order distributed Raman and first-order lumped Raman amplification.

We experimentally investigated and demonstrated an ultralow noise hybrid amplifier that combines second-order distributed Raman amplifier (DRA) and first-order lumped Raman amplifier (LRA) in a cascaded approach. This approach allows for the reutilization of pump light from the LRA as the seed light in the second-order DRA, and simultaneous full-band dispersion compensation is realized by using dispersion compensation fiber in the LRA. This approach also supports broadband gain flattening based on the separated DRA and LRA configuration. The transmission application of the proposed amplifier was investigated using a set of 10 external cavity lasers (ECLs) in the C-band and 8 ECLs in the L-band. Ranging from 1531.12 nm to 1595.49 nm across C + L band, the proposed hybrid amplifier gives a maximum on-off gain of 27.2 dB and an average gain of 23.4 dB, with an extremely low effective noise figure (NF) of lower than -2.9 dB. Intensity modulation direct detection (IMDD) signal transmission is carried out at two different data rates across these 18 wavelengths in the C + L band: (1) 56 Gbps/λ PAM-4 signal; (2) 112 Gbps/λ PAM-4 signal. The results show that the error free transmissions are demonstrated over 101.6 km EX2000 fiber using both signals with 7% HD-FEC and 20% SD-FEC, respectively.

Adiabatic propagation of beams in nonlocal nonlinear media with gradual linear loss/gain

The linear loss is a crucial factor in optical communications, which is unavoidable in actual physical system. To overcome the effect of the linear losses, the linear amplification of the optical fields is often conducted. However, the optical beam will shed partial energy, then cannot restore to its original state after one period of propagation. We investigate the evolution of optical beam in the nonlocal nonlinear media with linear loss and gain using the variational approach and the numerical simulation. When the linear loss gradually changes to the linear gain, the optical beams can restore to their initial states, the phenomenon we called the “adiabatic propagation”. We have demonstrated that, as long as the changing rate of the linear loss and gain is small enough, the linear gain can exactly compensate the linear loss and the adiabatic propagation can occur for any beams with any profiles. The numerical simulations agree well with the variational results. In experiment, this kind of linear gain can be realized by distributed Raman amplification.

Model-Aware XGBoost Method Towards Optimum Performance of Flexible Distributed Raman Amplifier

Toward the next-generation ultra-long-haul optical network, an extremely gradient boosting (XGBoost)-aided machine learning (ML) model is proposed to maximize the flexibility and uniformity in the performance of distributed Raman amplifier (DRA). In order to achieve an accurate prediction of desired signal gain spectrum and bit error rate (BER), a novel decision-tree based system is employed against inconsistent dimensionality between pump frequency and power. The impact of various model evaluation techniques: mean squared error (MSE), coefficient of determination (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ), root mean square measured data ratio (RSR) and the Nash-Sutcliffe coefficient (NSE) are discussed in detail. It is shown that the proposed method can diagnose the fault within 2.3 ms with accuracy of 99.6% and has also the highest estimation and efficacy in comparison with other ML based tree models. The reported work transforms the successful implementation of XGBoost model to estimate the desired gain profile and BER of DRA in low-loss optical wavelength region (1260-1650nm).

Pumping scheme for ultra-wideband WDM transmission using distributed Raman amplification

This paper describes the pumping schemes for ultra-wideband (UWB) WDM transmission using only distributed Raman amplification. By using numerical analysis based on the Gaussian noise model, we evaluate the amplification performances for all-Raman UWB-WDM transmission using higher-order pumping and/or forward pumping in addition to conventional 1st-order backward pumping. Moreover, we discuss the effect of forward Raman gain in 1st-order bidirectional pumping configuration, and clarify that the forward Raman gain should be carefully optimized taking account of both noise performance and nonlinear degradation.

Backward pumped distributed Raman amplifier: enhanced gain

The backward Raman amplifier (RA) can considered as one of the best solutions for optical communication, especially in Wavelength Division Multiplexing technology. They reduce the nonlinear effects, have low noise figure and a wide frequency range. The work in this paper aims to reduce the attenuation of optical signal due to its propagation optical fiber and increase both amplifier gain and output signal power. Two backward Raman models are proposed. Proposal one model consists of two cascaded RAs and the other (proposal two) consists of three cascaded RAs. Three backward pump power levels 200, 400, and 600 mW are used to simulate the models with the three types of fibers: single-mode fiber, Truewave, and Freelight, at an amplifier length of 100 km. Proposal two achieves a maximum gain of 31 dB at 600 mW pump power 600 mW using Truewave optical fiber, with 27.7 dBm maximum output signal power. This proposal is evaluated showing 11.15% gain enhancement and 200 mW saved power when compared to previously published work.

Technological Prospection and Requirements of 800G Transmission Systems for Ultra-Long-Haul All-Optical Terrestrial Backbone Networks

With the standardizations of 400GE and 400G completed or near completion, the attention is now refocused to next generation techniques with larger bit rates, i.e. 800G. We can see that current research commonly aims to short-reach or metro transmission for sharing key components with 400G, while ultra-long-haul transmission (typically ≥ 1500km) based on 800G is still in unknown state. Moreover, all-optical networking with OXC and ROADM is being gradually deployed all around the world, which further increases transmission performance requirement. According to past progress, it is urgent for us to analyze and clarify the requirements of 800G transmission systems for ultra-long-haul all-optical backbone networks. This work provides the technological prospection and requirements of 800G transmission systems for ultra-long-haul all-optical backbone networks. Firstly, the field network status and basic technical requirements for 800G are analyzed. Our record real-time 10-λ×800-Gb/s sub-carrier-multiplexing 95-GBd DP PCS-64QAM transmission over 2018-km G.654.E Fiber with pure backward distributed Raman amplification shows that reusing the components of current 400G technique is not the future direction. By numerically simulating the transmission performances of non-fully-loaded and fully-loaded DWDM scenarios, symbol rate higher than 180GBd, G.654.E, and optical bandwidth ≥ 12THz are necessary.

Demonstration and Characterization of High-Throughput 200.5 Tbit/s S+C+L Transmission over 2x100 PSCF Spans

Recent advances in multi-band amplification support ultra-wideband (UWB) systems as a suitable solution to cope with the increasing fiber communications traffic demand. The combination of UWB with spectral-efficient modulation formats can significantly increase in the total throughput of wavelength division multiplexed (WDM) transmission systems. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In this work, we demonstrate a 240×70 Gbaud PCS-256QAM WDM transmission using an optical bandwidth of 150 nm across the S, C and L bands. We combine doped-fiber amplifiers, semiconductor optical amplifiers (SOA) and backward distributed Raman amplification to achieve 200.5 Tbit/s of total generalized mutual information (GMI) throughput over two 100 km pure-silica-core fibers (PSCFs). We also present the digital twin of this experiment, providing the impact of wavelength-dependent impairments on the system performance. Our results demonstrate the feasibility of high-throughput multi-span UWB transmission.

Purely nonlinear amplified ultralow-noise transmission using hybrid second-order DRA and PPLN-based PSA.

We report ultralow-noise transmission over a 102-km single-mode fiber using a purely nonlinear amplification scheme consisting of a second-order distributed Raman amplifier (DRA) and a phase-sensitive amplifier (PSA) based on periodically poled LiNbO3 waveguides. The hybrid DRA/PSA features a broadband gain over the C and L bands and an ultralow-noise advantage, with a less than -6.3 dB effective noise figure in the DRA stage and a 1.6 dB optical signal-to-noise ratio (OSNR) improvement in the PSA stage. Compared with the unamplified link, the OSNR is improved by 10.2 dB for a 20-Gbaud 16QAM signal in the C band, resulting in error-free detection (a bit-error rate of less than 3.8 × 10-3) for the signal with a low link input power of -25 dBm. Mitigation of nonlinear distortion is also achieved by the proposed nonlinear amplified system due to the subsequent PSA.

Mitigating probe pulse deformation in Raman amplification in OTDR fiber sensing systems.

We report the numerical and experimental study of probe pulse deformation in a forward-pumped distributed Raman amplifier on a 40-km standard single mode fiber. Distributed Raman amplification can improve the range of OTDR-based sensing systems, but it could result in pulse deformation. A smaller Raman gain coefficient can be used to mitigate pulse deformation. The sensing performance can still be maintained by compensating for the decrease in the Raman gain coefficient by increasing the pump power. The tunability of the Raman gain coefficient and pump power levels are predicted while keeping the probe power below the modulation instability limit.

Asymmetry Optimization for 10 THz OPC Transmission over the C + L Bands Using Distributed Raman Amplification.

An optimized design for a broadband Raman optical amplifier in standard single-mode fiber covering the C and L bands is presented, to be used in combination with wideband optical phase conjugation (OPC) nonlinearity compensation. The use of two Raman pumps and fiber Bragg grating reflectors at different wavelengths for the transmitted (C band) and conjugated (L band) WDM channels is proposed to extend bandwidth beyond the limits imposed by single-wavelength pumping, for a total 10 THz. Optimization of pump and reflector wavelength, as well as pump powers, allows us to achieve low asymmetry across the whole transmission band for optimal nonlinearity compensation. System performance is simulated to estimate OSNR, gain flatness and nonlinear Kerr distortion.