Dispersion Compensation Fiber Research Articles

Michelson Interferometer-based Tunable Multiwavelength Thulium-doped Fluoride Fiber Laser in S-band for 5G networks

Abstract In this work, a multiwavelength thulium-doped fluoride fiber laser (TDFFL) has been reported for S-band region using the Michelson interferometer as an optical filter. Michelson interferometer was utilized as a comb-like filter, whereas dispersion-compensated fiber (DCF) of 10 km length was used to increase the number of lasing lines and reduce mode competition. Approximately, 61 lasing lines were achieved with a signal-to-noise ratio (SNR) of 40 dB in the wavelength region from 1501.36 to 1505.52 nm within 10 dB of maximum power. The stability of multiwavelength fiber laser was also recorded for the time duration of two hours, and it was found that all lasing lines were stable and equally spaced at the free spectral range (FSR) of 0.07 nm. The variation in optical power was less than 0.5 dB, however the wavelength shift was about 0.01 nm. Tunability of multiwavelength laser has also been observed up to the broader transmission span of 57 nm by incorporating the tunable band pass filter (TBPF). Moreover, FSR was observed to be tunable within the range of 0.02 to 0.14 nm by using the optical delay line (ODL) with a Michelson interferometer. Additionally, the proposed laser can generate frequency signals from 2.65 GHz to 18.54 GHz according to the obtained range of FSR.

Broadband dispersion compensation and high birefringence photonic crystal fiber for CWDM/DWDM networks

In this study, we propose a new design based on photonic crystal fibers (PCFs) for broadband dispersion compensation in telecommunication networks. The proposed design has a hexagonal structure arrangement of air-holes rings of different diameters between the silica core and the cladding. The PCF properties like effective area, nonlinearity, dispersion slope, confinement loss, and birefringence are reported and discussed. For the best performance we present three designs A, B and C. Simulation results show that the three designs cover the six-telecommunication optical bands O-, E-, S-, C-, L- and U- bands (wavelengths ranging from 1260 to 1675 nm). Design A achieves a large negative dispersion value of about − 1716 ps/(nm.km) with relative dispersion slope equals to that of conventional single-mode optical fibers (SMFs) of about 0.0036 nm−1, which makes it very suitable for long-haul DWDM transmission systems. With a little modification in the core, designs B and C achieve much higher confinement ability and achieve a very large birefringence value for polarization mode dispersion and sensing applications. Design C is engineered to have exact opposite dispersion of SMF with zero dispersion at the wavelength 1310 nm, which makes it a promising design in CWDM transmission system. The numerical values have been investigated using the full vector finite element method.

Optimizing High Data Rate Up to 2.5 Tbps Transmission using 64-Channel DWDM System with DCF and NRZ Modulation

Objectives: This study aims to enhance and optimize a modern communication system for high data rate transmission using Dense Wavelength Division Multiplexing (DWDM). The objectives include employing a 64-channel DWDM system, implementing different data speeds, and utilizing a dispersion compensation method. Methods: To achieve the objectives, we simulate and analyze the effects of Dispersion Compensation Fiber (DCF) in a DWDM system with 64 channels. The system employs Non-Return-to-Zero (NRZ) modulation format at varied bit rates and multiple energy levels. We propose a method for achieving data rates of 10 to 40 Gbps using NRZ modulation and Erbium-Doped Fiber Amplifier (EDFA) over a single-mode fiber transmission distance of 40 to 160 km, along with a dispersion compensation fiber of 8 to 32 km (DCF). The performance of the developed model is evaluated based on Quality Factor, Bit Error Rate (BER), Eye Height, and Threshold. These metrics are measured at two input energy levels from an optical power source, covering a communication capacity ranging from 0.625 Tbps to 2.5 Tbps. Findings: Through the simulations and analyses, we uncover the impact of dispersion and demonstrate the effectiveness of the proposed method in compensating for dispersion effects. Performance analysis of two different input transmitter power levels, -10 dBm is more efficient compared to 0 dBm input transmitter power in terms of bit error rate and quality factor. Novelty: This study presents a novel approach to improving modern communication systems by utilizing DWDM with a dispersion compensation method. The use of a 64-channel DWDM system, combined with the proposed NRZ modulation technique and dispersion compensation fiber, provides an efficient solution for achieving high data rates over long transmission distances while minimizing the effects of dispersion. The findings contribute to the advancement of communication systems for high data rate transmission. Keywords Dispersion effect, Bit Error Rate, Q-factor, Optisystem software, Erbium doped fiber amplifier

OSNR enhancement of Rayleigh-assisted Brillouin-Raman fiber laser via double pass configuration.

We propose and demonstrate a 10 GHz spacing multi-wavelength Brillouin-Raman fiber laser (MBRFL) with wide bandwidth and an outstanding optical signal-to-noise ratio (OSNR). This is achieved by utilizing loop mirror at one end of the laser cavity through a symmetrical bi-directional Raman pumping scheme. The setup is arranged in a double pass configuration by employing different lengths of dispersion compensating fibers (DCF). The attainment of MBRFL with outstanding performance necessitates the optimization of Raman pump power, Brillouin pump wavelength, and DCF length. By employing an 11 km DCF, when setting the Brillouin pump wavelength at 1531.4 nm, 504 Stoke lines are produced with a channel spacing of 0.08 nm. All the counted laser lines have less than a 1-dB peak amplitude variation and are spread across a 40.4 nm bandwidth that covers from 1531.4 to 1571.8 nm wavelength. In this case, the Raman pump power is fixed at 900 mW which results in average OSNR and Stokes peak amplitude level of 28 dB and -7 dBm respectively. To date, this is the simplest cavity design with the widest bandwidth and flattest spectrum together with outstanding OSNR attained in 10 GHz spacing multi-wavelength fiber lasers that incorporate a single low-power Raman pump unit.

Interferometric fiber sensor for lead ion detection based on MoS2 hydrogel coating

A fiber optic sensor coated with molybdenum disulfide (MoS2) hydrogel is firstly proposed for the detection of lead ion (Pb2+). By splicing a dispersion-compensating fiber (DCF) between two single-mode fibers (SMFs) to form a Mach-Zehnder interferometer (MZI), and using a fusion splicer to discharge the SMF input and output to form a thick waist cone to act as a coupler. A portion of the DCF cladding is etched to excite higher order cladding patterns and a hydrogel sensing film is applied to the etched area, the sulfur atoms in the sensing film form coordination bonds with Pb2+ and change the refractive index (RI) of the sensing film, which further leads to the wavelength shift of the resonant dip. The production process is simple and environmentally friendly. By monitoring the wavelength shift, the adsorption of Pb2+ is continuously monitored, and the sensor has a sensitivity of 3.25 × 108 nm/(mol/L) in the range of 0–1.1 × 10−8 mol/L Pb2+ in aqueous solution. The theoretical detection limit of Pb2+ concentration is 6.15 × 10−11 mol/L at a spectrometer resolution of 0.02 nm. In addition, the experimental results show that the sensor has good repeatability, selectivity and stability, and has a broad application prospect in the field of Pb2+ detection in industry and agriculture.

Orbital angular momentum mode femtosecond fiber laser with over 100 MHz repetition rate

Orbital angular momentum (OAM) lasers have potential applications in large capacity communication systems, laser processing, particle manipulation and quantum optics. OAM mode femtosecond fiber laser has become the research focus due to the advantages of simple structure, low cost and high peak power. At present, OAM mode femtosecond fiber lasers have made some breakthroughs in key parameters such as repetition frequency, pulse width, spectrum width, but it is difficult to achieve good overall performance. Besides, the repetition rate is tens of MHz at present. In this paper, a large-bandwidth mode coupler is made based on the mode phase matching principle. In coupler, the first order mode coupler with 3 dB polarization dependent loss is made by the technology of strong fused biconical taper, and the second order mode coupler with 0.3 dB polarization dependent loss is made by the technology of weak fused biconical taper. By combining the nonlinear polarization rotation mode-locking mechanism, OAM mode femtosecond fiber laser with over 100 MHz repetition rate is built. The achievement of the key parameters is attributed to the selection of dispersion shifted fibers that can accurately adjust intracavity dispersion. Comparing with traditional dispersion compensation fibers (DCF), the group velocity dispersion is reduced by an order of magnitude, so it can better adjust intracavity dispersion to achieve the indexes of large spectral bandwidth and narrow pulse width. In addition, the diameter of the fiber is 8 μm, which is the same as that of a single mode fiber. Comparing with DCF, the fusion loss can be ignored, so only a shorter gain Erbium-doped fiber is required, which ensures a shorter overall cavity length and achieves high repetition frequency. The experimental results show that the first order OAM mode fiber laser has 113.6 MHz repetition rate, 98 fs half-height full pulse width, and 101 nm 10 dB bandwidth. Second-order OAM mode fiber laser has 114.9 MHz repetition rate, 60 fs half-height full pulse width, and 100 nm 10 dB bandwidth. Compared with the reported schemes, our scheme has good performance in key parameters such as repetition rate, pulse width and spectral width. We believe that the OAM mode fiber laser with excellent performance is expected to be widely used in OAM communication, particle manipulation and other research fields.

Narrowband all-fiber acousto-optic tunable add-drop filter based on dispersion-compensating fiber

Narrowband all-fiber acousto-optic tunable add-drop filter based on dispersion-compensating fiber

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.

Switchable noise-like pulse generation in an all-polarization-maintaining thulium-doped fiber laser

In this paper, a tuning method based on temperature control of a piece of polarization-maintaining dispersion compensation fiber (PMDCF) is proposed in an all-polarization-maintaining (all-PM) thulium-doped fiber laser. The proposed tuning method simplifies the tuning parameter of the all-PM fiber laser, and various patterns of noise-like pulse (NLP) output can be realized only by adjusting the temperature of the PMDCF. The rectangular-shaped NLP, NLP bunches, the coexistence of rectangular-shaped NLP and NLP bunches, double rectangular-shaped NLP, and the switching between them are observed only through changing the temperature of the PMDCF, which helps to improve the research on the underlying physical mechanism of NLP. To the best of our knowledge, this is the first report of various patterns of NLP and their switching phenomena in an all-PM thulium-doped fiber laser.

Optimization technology for DCF dispersion compensation based on cascaded fiber Bragg grating.

A cascaded fiber Bragg grating (FBG) structure is proposed to reduce the dispersion of optical signals in single-mode fibers. Using the OptiSystem software for simulation, the three compensation schemes (precompensation, postcompensation, and symmetric compensation) of dispersion-compensated optical fiber (DCF) are analyzed, and the results show that the best of the three schemes is the postcompensation structure. For the postcompensation scheme, the influence of the coding method and duty cycle on the system is analyzed, and then the fiber grating is cascaded behind the transmitter to obtain a narrow linewidth of the optical signal and minimize the reflectivity sidelobe, and a chirped fiber grating is connected in front of the receiver to compensate for the dispersion of the channel residue. With or without cascaded FBGs, system performance at different input powers and different transmission distances is discussed. The results show that cascading fiber gratings can improve the performance of the system.

Ultra-Wide Bandwidth Brillouin-Raman Random Fiber Laser With Augmented Synergistic Nonlinearity

We propose a Brillouin-Raman random fiber laser with enhanced synergistic nonlinearity for ultra-wide bandwidth Brillouin comb generation. The augmented synergistic nonlinearity, including enhanced Rayleigh scattering (RS) effect, stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS), is achieved in a hybrid fiber (a fiber combination of a 7.2-km dispersion compensation fiber and a 10-km single-mode fiber) under a strong Raman pumping condition. Under the strong Raman pumping condition, more Stokes lines are generated due to the enhanced RS-induced oscillations of Brillouin Stokes lines at short wavelength band, thus suppressing self-lasing cavity mode oscillations at long wavelength band. In the experiments, the multi-wavelength Brillouin comb with an ultra-wide bandwidth of 63.5 nm (1513 nm-1576.5 nm) with frequency spacing of double Brillouin frequency shift, which is the largest bandwidth from Brillouin fiber lasers, to the best of our knowledge, has been achieved. The proposed ultra-wide bandwidth Brillouin-Raman fiber laser has potential applications in optical communication, optical wavelength division multiplexing, and fiber sensing.

Refractometer based on extinction ratio demodulation using no-core and dispersion-compensating fiber structure

A simple and cost-efficient fiber sensor based on multi-mode interference and core diameter mismatch technologies is proposed to detect the refractive index (RI) in this paper. The refractometer is fabricated by embedding a section of no-core fiber between a section of multimode fiber and dispersion-compensating fiber. Since the power distribution in the fiber will change with the effective refractive index of the cladding, the extinction ratio can be used to characterize the RI sensitivity. The experimental results show that a linear response is obtained with a RI sensitivity of 392.585 dB/RIU in the range of 1.333–1.374. Featured with high sensitivity, simple construction, easy fabrication, low cost and good repeatability, the novel refractometer has potential applications in practical chemical detecting and portable biological sensing.

Single-longitudinal-mode narrow linewidth broadband tunable Brillouin random laser including dispersion compensation fibers

We propose and demonstrate a single-longitudinal mode (SLM) narrow linewidth broadband tunable Brillouin random laser, including two segment dispersion compensated fibers (DCFs), in which enough narrowband Brillouin gain provided by a 2-km-length DCF to overcome the cavity loss, and Rayleigh backscattering (RBS) provided by a 1-km-length DCF form a mirrorless open cavity to continuously compress the laser linewidth. Compared to ordinary single mode fibers, DCF has an enhanced stimulated Brillouin scattering gain coefficient and RBS coefficient, which is attributed to its small core diameter structure, making the laser more compact and stable. Stronger random feedback effectively lowers the laser threshold, and enough Brillouin gain for multiple amplifications in random mode makes SLM operations more accessible. The proposed laser is with a threshold of ∼11 mW and an optical signal-to-noise ratio (OSNR) of ∼55.75 dB, the 3-dB linewidth and linewidth compression ratio of the output laser reaches ∼550 Hz and ∼236, respectively. By changing the wavelength of the pump laser, the laser wavelength can be continuously tuned in a broad wavelength range, which is only limited by tunable range of Brillouin pump laser. The laser wavelength fluctuation of 0.02 nm and the OSNR fluctuation of about 3 dB in a 30-minute measure period, indicating that the laser is with a good stability.

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.

Design of Ultra Dense WDM Optical Communication System to Reduce Signal Impairments Using DCF and Repeater Techniques

Linear and non-linear impairments are the major problems that affected the dense wavelength division multiplexing (DWDM) system performance. In this simulation designs, two different compensation techniques have been proposed to eliminate signal impairments. The repeater technique was proposed to reduce non-linear effects like four-wave mixing (FWM) which cause transfer power from DWDM channels to another new channels. The dispersion compensation fiber (DCF) technique was used to reduce dispersion effects which cause signal pulse broadening over long transmission distances. Also, three different modulation formats and four frequency separations were used to determine which modulation scheme is more compatible with the compensation techniques. The results is calculated in term of quality factor against power and noetic that the carrier suppressed return to zero (CSRZ) format offers the best performance with the DCF technique with 32.1804 Q-factor at 15dBm threshold power then, the differential phase shift keying (DPSK) format is compatible with the repeater technique with 27.7959 quality factor and 14dBm threshold power. Index Terms— Dense Wavelength Division Multiplexing (DWDM), Dispersion Compensation Fiber DCF, Repeater, and Non-linear Effects.

Broadband dual-chirp FMCW laser source based on DSB-SC modulation and cascaded FWM.

Based on dual-sideband suppressed-carrier (DSB-SC) modulation and two-stage cascaded four-wave-mixing (FWM), a scheme of broadband dual-chirp frequency-modulated continuous-wave (FMCW) laser source is proposed and experimentally demonstrated. First, via a Mach-Zehnder modulator biased at its null point, an original DSB-SC FMCW signal with 4.0 GHz swept-frequency range and 0.2 GHz/μs sweep rate is generated. Next, the original DSB-SC FMCW signal is sent to a 1 km dispersion compensation fiber for implementing first-stage FWM, a dual-chirp FMCW signal with 12.0 GHz swept-frequency range and 0.6 GHz/μs sweep rate is acquired and used as the pump for second-stage FWM. Finally, via second-stage FWM in a 200 m highly nonlinear fiber, a dual-chirp FMCW signal with a swept-frequency range of 36.0 GHz and sweep rate of 1.8 GHz/μs is generated. Taking the FMCW signal generated at different stages as the emitted signal, we evaluate the ranging resolution through fiber-based distance measurement, and the results demonstrate that the achieved ranging resolutions are 5.31 cm, 2.04 cm, and 1.18 cm, respectively. Through equalizing the optical power of generated FMCW signal over the swept-frequency range, the ranging resolution can be further improved.

In-band full-duplex multiband mobile fronthaul network based on analog radio-over-fiber andtandem SSB modulation.

An in-band full-duplex multiband mobile fronthaul network is proposed based on analog radio-over-fiber and tandem single-sideband (TSSB) modulation. Two optical carriers with a wavelength spacing of 50GHz in accordance with international telecommunication union dense wavelength division multiplexing (DWDM) standards are employed in each distributed unit (DU): one is used to carry two different radio frequency (RF) vector signals at 3 and 10GHz, while the other is used to carry a vector signal at 15GHz and a single-tone signal at 15GHz. At the DU, a parallel TSSB modulation is applied, which eliminates the cross talk of TSSB modulation through two dual-polarization binary phase-shift keying (DP-BPSK) modulators. This allows the two vector signals carrying different data to be distributed on both sides of the optical carrier. At the active antenna unit (AAU), different RF vector signals centered at 3, 30, and 60GHz, each carrying distinct information, can be generated by selecting either one DWDM channel or two adjacent DWDM channels in a group. By utilizing the spacing between the two DWDM optical carriers, millimeter-wave signals can be generated without the need for additional electronic upconversion devices in the AAU. In the uplink, a DP-BPSK modulator is used to receive the signal of interest while canceling self-interference. Simulation results demonstrate the performance of the proposed system. After transmitting 25km through single-mode fiber and compensating for dispersion using corresponding dispersion-compensating fiber, the downlink and uplink achieve error vector magnitudes of less than 9% and 2%, respectively, when the receiving optical power is 6dBm.

Study of transition dynamics from breathing single pulse to higher-order pulses and hysteresis in a figure-of-9 fiber laser

This study investigates the nonlinear dynamics and hysteresis phenomena in a figure-of-9 fiber laser. The laser cavity consists of an Erbium doped nonlinear amplifying loop mirror (NALM) containing a Dispersion Compensation Fiber (DCF) segment, coupled to a nonlinear optical loop mirror (NOLM). A lumped-element model is developed for the laser cavity accounting for bi-directional light propagation. The model is based on the modified nonlinear Schrödinger equation (NLSE) with coefficients directly related to the parameters of each cavity segment. Gain saturation is taken into consideration for stable laser operation. The numerical results show that self-starting passive mode-locking and self-structuration of soliton lattices occur in the cavity of the laser. The soliton structuring is based on the concept of dissipative solitons, which requires a balance between dispersion-nonlinearity and gain-loss. The gain-loss parameters influence both the temporal pulse interactions and the NALM’s transmission, leading to a large variety of single and multiple breathing dissipative soliton dynamics. In that context, riveting studies of the transition dynamics from breathing single pulses to high-order multiple breathing dissipative solitons and hysteresis with respect to unsaturated amplifier gain in a figure-of-9 all-fiber laser are explored.

Microwave Frequency Dissemination over a 250 km Fiber Link with Stability at the 10−18 Level

In this paper, a microwave phase compensation scheme is adopted. It utilizes microwave signals of different frequencies for round-trip signal transmission over a 250 km fiber optic link to mitigate the impact of parasitic reflections. Additionally, dispersion compensation fibers are employed to compensate for the dispersion in the fiber optic link. Bidirectional optical amplifiers are utilized to compensate for the losses in long-distance fiber optic links and reduce optical path asymmetry. By implementing these methods, the transmission stability of the fiber optic microwave frequency transmission system achieves 5.6 × 10−15 at 1 s and 2.8 × 10−18 at 100,000 s.

Flatness enhancement of multi-wavelength Brillouin-Raman fiber laser with 10 GHz spacing utilizing Raman pump power distribution.

A simple high flat amplitude multi-wavelength Brillouin-Raman fibre laser (MBRFL) with 10 GHz spacing and excellent optical signal-to-noise ratio (OSNR) in C-Band spectral region is demonstrated. The laser consists of a linear cavity in which 12 km dispersion compensating fiber (DCF) in addition to 49 cm Bismuth-oxide Erbium doped fiber (Bi-EDF) are employed as a gain medium for amplification. The impact of Raman pump power distribution through changes in coupling ratio on amplitude flatness is carried out by comparing the peak power discrepancy between odd- and even-order Brillouin Stoke lines. This is the main property that allows the efficient controlling of gain propagation between lasing lines that is vital for Stokes flattening initiation and other output spectra characteristics. The attainment of MBRFL with outstanding OSNR necessitates the utilizing of Bi-EDF as a noise suppressor. By utilizing a 50/50 coupler, 354 identical channels together with uniform Brillouin Stokes linewidth within only 0.3-dB maximum power difference between adjacent channels is generated. The average OSNR and Stokes power are 28 dB and -5 dBm respectively when the RPP is set at 1300 mW. To date, this is the highest flatness 10 GHz spacing MBRFL with outstanding OSNR attained in MBRFL that incorporate only a single Raman pump unit.