Negative Dispersion Fiber Research Articles

Bi-directional SMF-NDF-optical/5G NR wireless converged systems

This study presents the transmission of fifth-generation (5G) new radio (NR) signals over bi-directional single-mode fiber (SMF)-negative dispersion fiber (NDF)-optical/5G NR wireless converged systems, using two cascaded reflective semiconductor optical amplifiers (RSOAs). Downstream transmission of 5G NR 16-quadrature amplitude modulation (QAM) signals achieved an aggregate net bit rate of 228.037 Gb/s, comprising 59.813, 74.766, and 93.458 Gb/s at 150, 250, and 325 GHz, respectively. The system achieved a low bit error rate (BER) and clear constellation patterns. However, systems without NDF exceed the forward error correction 7% threshold, indicating the importance of NDF in compensating for fiber dispersion. Moreover, for upstream transmission, two cascaded RSOAs are used to transmit 5G 16-QAM-orthogonal frequency division multiplexing signals, achieving a total data rate of 40 Gb/s. The use of two cascaded RSOAs in the system significantly improved upstream performance, resulting in low BERs and clear constellation patterns. This system not only achieved high data rates but also extended transmission coverage to support the deployment of advanced 5G NR applications.

Nonlinear noise suppression in a high-rate optical channel with phase modulation and dispersion compensation

We have performed a numerical simulation of transmission of optical DP QPSK signals at a rate of 40 Gbaud over a distance of 2000 km. It is shown that a channel with large negative dispersion and preliminary large positive pulse chirping significantly reduces nonlinear distortion and improves the signal quality. To further reduce the probability of recognition error, it is proposed, instead of a negative dispersion fibre, to use compensators with low attenuation.

1060 nm Single-Mode VCSEL and Single-Mode Fiber Links for Long-Reach Optical Interconnects

We investigate the use of a 1060 nm single-mode vertical-cavity surface-emitting laser (VCSEL) and a 1060 nm single-mode fiber as a competitive single-mode technology for cost- and power-efficient long-reach optical interconnects. Error-free transmission (bit error rate < 10–12) over 2 km is demonstrated at bitrates up to 40 Gb/s under on-off keying non-return-to-zero (OOK-NRZ) modulation, without equalization, forward-error correction, or other forms of digital signal processing. The VCSEL is extensively characterized with respect to its static and dynamic performances, including the power–voltage–current characteristics, spectral characteristics, beam divergence, modulation response, relative intensity noise, and frequency chirp. The measured dependence of power penalty on fiber length is consistent with an analysis of chirp-induced pulse compression and broadening along the negative chromatic dispersion fiber.

Cost Efficient 4 × 2.5 Gb/s Transparent WDM Ring Network using DML and MetroCor Fiber for Long Reach Applications

Abstract In this paper, we analyze the performance of the 4 × 2.5 Gb/s wavelength division multiplexing (WDM) transparent metro ring network comprising of one network node and eight access nodes. Here, the power requirement of 360 km ring network has been evaluated using the optical signal to noise ratio (OSNR), Q-factor, inter-symbol interference (ISI) and power penalty. The metro network utilized the cost-effective directly modulated laser (DML) and a negative dispersion fiber called MetroCor in order to give enhanced performance in terms of Q-factor. The power requirement of the network is optimized for the signals over SMF-28 and MetroCor fibers. Also, the comparison is drawn between uncompensated and compensated (with -post and -symmetrical) SMF-28 fibers in the metro environment. The excellent value of Q-factor is obtained at all the nodes. Also, the results show higher OSNR values in the metro environment. Although, smaller power penalties are detected for nodes closer to the network node, but distant nodes require higher power for better transmission.

Influence of modulation instability on the operation of phase-sensitive optical time domain reflectometers

Modulation instability (MI) in optical fibers adversely affects performance of phase-sensitive optical time domain reflectometers causing reduction of statistical visibility of the coherent reflectograms and corresponding degradation of the phase sensitive signal. This effect limits intensity of the probing pulse and imposes limits on the reflectometer operational range. Intensity limits imposed by the MI development were quantified for different positive dispersion fibers using nearly rectangular ~200 ns pulses at 1.5 µm wavelengths. MI development and reversible character of energy exchange between narrowband probing pulse and wideband optical noise known as Fermi–Pasta–Ulam energy recursion were observed. It is demonstrated both experimentally and numerically that the operational range of coherent reflectometers can be extended by increasing probing pulse energy if negative (normal) dispersion fibers are used, where MI development is suppressed.

A scheme of pulse compression lidar with enhanced modulated bandwidth for detection through scattering media

This paper presents a scheme of pulse compression lidar with enhanced electrical modulated bandwidth. An ultra-wideband linear frequency modulated signal with a bandwidth of 50GHz is generated using femtosecond laser and superimposed linear chirp fiber Bragg gratings in the transmitter, which separates the echo of the target from the backward scattered noise with low modulated frequency. An optical pulse compression system based on a negative dispersion fiber Bragg grating is used to compress the ultra-wideband linear frequency modulated signal in the receiver. SNR and range resolution of the proposed scheme are numerically simulated to prove its feasibility. The simulation results indicate that an enhancement of SNR by 15.8dB can be achieved using the scheme, and the range resolution of the scheme increases from 0.68m to 0.0027m. It is therefore concluded that the proposed scheme is suitable for detection through scattering media.

一种高双折射高负平坦色散压缩型光子晶体光纤

一种高双折射高负平坦色散压缩型光子晶体光纤

一种高双折射高负平坦色散压缩型光子晶体光纤

一种高双折射高负平坦色散压缩型光子晶体光纤

A 20 km/80 Gbps bidirectional PON employing three-stage injection-locked VCSELs/NDFs/OBPFs

A 20 km/80 Gbps bidirectional passive optical network (PON) employing three-stage, injection-locked, 1.55 μm, vertical-cavity surface-emitting lasers (VCSELs), negative dispersion fibers (NDFs), and optical band-pass filters (OBPFs) is proposed and demonstrated. The three-stage injection-locked technique, which can greatly increase the frequency response of VCSELs, is thereby expected to provide excellent transmission performance in a bi-directional PON. To be the first one of employing directly modulated, three-stage injection-locked, 1.55 μm, VCSELs; NDFs; and OBPFs results in excellent bit error rate (BER) performance, and clear eye diagrams are obtained for 20 km/80 Gbps, bidirectional PON applications. Such a novel bidirectional PON provides the advantage of a communication link for high data rates that could accelerate bidirectional PON deployment.

A 20-km/60-Gb/s Two-Way PON Based on Directly Modulated Two-Stage Injection-Locked 1.55- &lt;inline-formula&gt; &lt;tex-math notation="TeX"&gt;$\mu\hbox{m}$&lt;/tex-math&gt;&lt;/inline-formula&gt; VCSEL Transmitters and Negative Dispersion Fibers

A 20-km/60-Gb/s two-way passive optical network (PON) based on directly modulated two-stage injection-locked 1.55-μm vertical-cavity surface-emitting laser (VCSEL) transmitters and negative dispersion fibers (NDFs) is proposed and demonstrated. A one-stage injection-locked technique has been confirmed as an effective approach for increasing the frequency response of a VCSEL. A two-stage injection-locked technique, which can further increase the frequency response of a VCSEL, is thereby expected to have excellent transmission performance in a two-way PON. To be the first to employ directly modulated two-stage injection-locked 1.55-μm VCSEL transmitters in a two-way PON, brilliant bit-error-rate performance and a clear eye diagram are obtained over a 20-km NDF transport. A directly modulated VCSEL has a positive chirp, whereas an NDF has a negative dispersion property in the transmission fiber; this negative dispersion property compensates the laser positive chirp and results in systems with better transmission performance. Such an innovative two-way PON provides the advantage of a communication link for high data rates, which is an attractive feature that is useful for broadband network applications.

Lumped Time-Delay Compensation Scheme for Coding Synchronization in the Nonlinear Spectral Quantization-Based All-Optical Analog-to-Digital Conversion

In this paper, we propose a novel lumped time-delay compensation scheme for the all-optical analog-to-digital conversion based on soliton self-frequency shift and optical interconnection techniques. By inserting a segment of negative dispersion fiber between the quantization and the coding module, the time delay of different quantized pulses can be accurately compensated with a simple structure compared to the multiple time-delay lines. The simulation results show that the coding pulses can be well synchronized using a span of fiber, with the flattened negative dispersion within the wavelength range of 1558-1620 nm. In addition, the problems of pulse broadening and time error are discussed, and it is shown that no damage happens to the coding correctness within the sampling rate of 30 GSa/s.

Dual-wavelength step-like pulses in an ultra-large negative-dispersion fiber laser

We report on experimental observation of dual-wavelength step-like pulses delivered from an erbium-doped fiber laser operating in ultra-large negative-dispersion regime. The step-like pulses consist of two rectangular pulses with different energies, durations as well as optical spectra, and are distinct from the conventional multi-solitons or bound-state solitons in that each pulse holds the same property. We find the weaker (or stronger) rectangular pulse in step-like pulses is more sensitive to the backward (or forward) pump while is less sensitive to the forward (or backward) pump. Our results demonstrate that the dual-wavelength operation results from the combination of fiber dispersion, fiber birefringence, as well as cavity filtering effect, and the intensity difference between rectangular pulses can be attributed to different gain characteristics of the forward and backward pump.

Negative Power Penalties of Optical OFDM Signal Transmissions in Directly Modulated DFB Laser-Based IMDD Systems Incorporating Negative Dispersion Fibers

Detailed investigations of dynamic negative power penalty characteristics of optical orthogonal frequency division multiplexing (OOFDM) signal transmissions are undertaken, for the first time, in directly modulated distributed feedback (DFB) laser (DML)-based intensity modulation and direct detection (IMDD) systems incorporating negative dispersion fibers such as MetroCor fibers. Excellent agreements between numerical simulations and real-time experimental measurements are obtained over a wide diversity of transmission conditions of the aforementioned systems. The physical mechanism underpinning the occurrence of negative power penalties is the reduction in subcarrier intermixing impairment due to the compensation between DML positive frequency chirps and MetroCor negative chromatic dispersions. It is also shown that the negative power penalty is independent of both cyclic prefix and signal modulation format and, more importantly, controllable when adaptive modulation and/or appropriate adjustments of DML operating conditions are applied.

Externally modulated CATV/ROF transport systems based on negative dispersion fiber

An externally modulated lightwave cable television (CATV)/radio-over-fiber (ROF) transport system based on negative dispersion fiber (NDF) as the transmission medium is proposed and demonstrated. Good performances of carrier-to-noise ratio (CNR), composite second-order (CSO) and composite triple beat (CTB) were obtained for the CATV signals; low bit error rate (BER) and third-order intermodulation distortion to carrier ratio (IMD3/C) values were achieved for ROF applications. The negative dispersion property compensates the positive chirp and results in systems with better transmission performances.

Enhanced performance of WDM systems using directly modulated lasers on positive dispersion fibers

Cost-effective directly modulated distributed feedback lasers (DML) have attracted much attention recently for operation at the 1.55 μm wavelength band applications in metropolitan area networks. In this paper, we show by simulation that the effect of directly modulated laser chirp can be compensated by a negative dispersion fiber, but this only occurs in a specific range of DML output power, and that a pulse broadened by the positive dispersion fiber can be equalized using self-phase-modulation (SPM) in optical fiber. The majority of metro and access networks are made up of conventional single-mode fibers (SMF) which are positive dispersion fibers. We demonstrated that optimum compensation is always feasible for such fibers, since the magnitude of the SPM can be controlled by changing the optical power in the fiber. Furthermore, simulation suggests that this technique will enable directly modulated wavelength division multiplexed systems to enhance their performance if the power of each channel is appropriate.

Numerical Study on High-Speed Optical RZ Pulse Transmission in Fiber Link With Dispersion-Slope Management

This paper presents a numerical study of the transmission of a 160-Gb/s return-to-zero pulse train in a fiber link, in which both the dispersion and the dispersion-slope are periodically compensated. Two types of slope-compensation are considered: one is lumped compensation at each repeater, and the other is distributed compensation that uses a slope-reversed negative dispersion fiber. It is predicted that distributed slope compensation will provide better performance than lumped slope compensation at each amplifying repeater. This tendency will hold irrespective of the strength of dispersion-management, though the strong dispersion-management will shorten the available transmission distance.

Directly modulated lasers in negative dispersion fiber links

AbstractIn the paper the impact of frequency chirp of directly modulated lasers is considered in context of high-speed data transmission over negative dispersion fiber. Chirp/dispersion induced signal distortions are described, and detailed investigations of their influence on 10 Gb/s transmission system performance are presented. The desired laser chirp characteristics and optimal driving conditions are determined. It is also demonstrated that directly modulated laser with low chirp offers similar or even better dispersion tolerance than unchirped (externally modulated) source. Experimental verification of described investigations is presented at the end.

Comparison of various dispersion-compensation techniques in a cable television system

Various dispersion-compensation techniques are compared on the basis of eye opening, eye closure, bit error rate, and Q-factor. The techniques that use dispersion-compensating fiber, fiber Bragg gratings (FBG), optical phase conjugators (OPC), negative dispersion fiber (NDF), and reverse dispersion fiber (RDF) for dispersion compensation are compared. The NDF technique is more attractive for long-distance cable television (CATV) systems as this technique gives better eye opening, eye closure, bit error rate, and Q-factor characteristics than any other technique. The RDF technique is the next-best technique. The FBG technique is attractive only at a 120 km transmission distance in CATV systems. The OPC technique is not recommended for long-distance CATV transmission systems.

Long-Wavelength Vertical-Cavity Surface-Emitting Lasers on InP With Lattice Matched AlGaInAs–InP DBR Grown by MOCVD

1.3- and 1.55- $mu$ m vertical-cavity surface-emitting lasers (VCSELs) on InP have been realized. High-reflectivity AlGaInAs–InP lattice matched distributed Bragg reflectors (DBRs) were grown on InP substrates. 1.7 (for 1.3 $mu$ m) and 2.0 (for 1.55 $mu$ m) mW single mode power at 25 $^circ$ C, 0.6 mW single mode power at 85 $^circ$ C and lasing operation at $≫hbox100^circ$ C have been achieved. 10 Gbit/s error free transmissions through 10 km standard single mode fiber for 1.3- $mu$ m VCSELs, and through 15 km nonzero dispersion shift fiber for 1.55- $mu$ m VCSELs, have been demonstrated. With the addition of an SOA, 100 km error free transmission at 10 Gbit/s also has been demonstrated through a negative dispersion fiber. No degradation has been observed after over 2500-h aging test.

40-gb/s transmission over 25 km of negative-dispersion fiber using asymmetric narrow-band filtering of a commercial directly Modulated DFB laser

Using asymmetric narrow-band optical filtering to improve the response and reshape the optical spectrum of a commercial directly modulated distributed feedback laser, we demonstrate 40-Gb/s error-free transmission over 25-km negative dispersion fiber without dispersion compensation.