Dispersion Compensation Fiber Research Articles

A tradeoff for dispersion compensating fibers (DCFs) deployment in SAC-OCDMA environment using 2D-Fixed Right Shift (2D-FRS) code

This paper presents design and implementation of a new two-dimensional fixed right shifting (2D-FRS) code in optical code-division multiple access (OCDMA) systems. The proposed code employs spatial domain in combination with spectral encoding to elevate orthogonality between the adjacent codes. In comparison with the existing 2D coding schemes, 2D-FRS not only reserves the multiple interference-cancellation property, but also provides better performance against the effects of shot, thermal and phase-induced intensity noise. Investigation of the proposed system using numerical and simulation approach shows that larger number of simultaneous users can be supported by 2D-FRS system in comparison with existing counterparts under given bit-error-rate (BER). This paper further examines the effect of dispersion on performance of 2D-FRS based OCDMA system due to the use of numerous fiber strands between the transmitter and receiver modules for spatial encoding operation. Investigation is made in terms of data rate, fiber span and channel spacing. Analysis using a highly recognized software called OPTISYSTEM verifies that the proposed system is able to support data rates of up to 32 × 1 Gbps without employing dispersion compensation fibers (DCFs). It is also shown that application of DCF can further negate MAI and support higher transmission capacity leading to a tradeoff between the limited dispersion effects and the MAI.If g = 0 ∩ h ≠ 0 and h = 0 ∩ g ≠ 0, hence RI(1)(g,h) and RI(2)(g,h) have nonzero value. This can be used to remove the effect caused by Ag,h with g = 0 ∩ h ≠ 0 and g ≠ 0 ∩ h from RI(0)(g,h). Deducting Eqs. (7) and (8) from Eq. (6), Eq. (9) is attained as follows

A hybrid DCF/FBG scheme for dispersion compensation over a 300 km SMF

In this work, the efficient restoration of a dissipated signal over a 300 km long-haul optical fiber is investigated. A hybrid system is proposed including a dispersion compensation fiber (DCF) and a fiber Bragg grating (FBG). Two 150 km standard single mode fibers with a chromatic dispersion of 17 ps/nm km are used in the simulation. Sufficient optical amplification power is supplied using an erbium-doped fiber amplifier to overcome the signal attenuation down the link, yet the signal is totally distorted. The only major reason left interpreting the total data loss would be the chromatic dispersion (CD). A DCF and a-tanh-apodized-linearly-chirped fiber Bragg grating (ACFBG) are implemented individually in a symmetric or a distributed setting in an attempt to compensate for the CD that led mainly to the signal degradation. The proposed hybrid scheme is then tested in a pre, post, symmetric and distributed installations. Several lengths of DCFs and ACFBGs at various parameters are examined. A comparison between the mentioned schemes is performed, seeking the most remarkable, resilient, and cost-effective technique.

An optical frequency-hopping scheme based on phase modulator-embedded optical loop mirror

An optical frequency-hopping scheme using phase modulator-embedded optical loop mirror (PME-OLM) is proposed, analyzed and demonstrated to achieve long distance secure communications. In the proposed system, the data from every user are separated into small data segments in time domain and carried by different wavelength carriers instead of being fixed on one carrier all the time. The segments from different users occupy different wavelengths at different time according to the hopping pattern, which can be regarded as encryption key. Therefore, any particular user data are interference to data from other users. The feasibility and performance of the frequency-hopping scheme has been investigated through simulation by VPI transmission Maker. A 4-frequency-hopping system demonstration was designed to support a 20 Gb/s non-return-to-zero (NRZ) data error-free transmission through 8-km dispersion compensated fiber (DCF) and 32-km single mode fiber (SMF). And an analysis based on a theoretical model was established to evaluate the security performance of the frequency-hopping communication system.

PAM4 transmission over 360 km of fibre using optical phase conjugation

We demonstrate the transmission of 3 × 20 Gbaud PAM4 signals over a 360 km, field-deployed, amplified transmission link. We compare dispersion compensation using optical phase conjugation (OPC) to dispersion compensating fibre (DCF) and find an improvement in the received bit error ratio of an order of magnitude using our OPC implementation.

Performance Signature of Optical Fiber Communications Dispersion Compensation Techniques for the Control of Dispersion Management

Abstract This paper has deeply simulated the different configurations of pre, post, and symmetric dispersion compensation-based dispersion compensated fiber (DCF), Gaussian optic filter (GOF), and fiber Bragg grating. Output power, signal quality factor, and signal gain are the performance parameters in this study for the complete comparison for the proposed techniques for dispersion compensation. It is observed that FBG has presented the best performance parameters optimization in compared to other compensation techniques for different configurations of compensation. The FBG dispersion compensation technique is the key solution for dispersion compensation in compared with other compensation techniques that are comparatively as in previous section. It is observed that the FBG is the best dispersion compensation technique and change its location, and length, apodization, and chirp functions, to obtain the best performance of FBG and give the best quality factor, output power, and gain, FBG can be employed in different categories such as post compensation, pre compensation, and symmetric compensation with different FBG lengths, apodization, and chirp functions.

IMDD Transmission at Net Data Rate of 333 Gb/s Using Over-100-GHz-Bandwidth Analog Multiplexer and Mach–Zehnder Modulator

We demonstrate intensity-modulated direct-detection optical transmission at a record-high data rate with single wavelength and single polarization. The high data rate is achieved with simple optics by using electronic and electrooptic devices with large operation bandwidths. We use a digital-preprocessed analog-multiplexed digital-to-analog converter with a >100-GHz analog multiplexer (AMUX) to drive an 80-GHz Mach–Zehnder optical modulator (MZM). The AMUX is based on 0.25-μm-emitter-width InP heterojunction bipolar transistor technology, and the MZM has InP n-i-p-n heterostructure optical waveguides with capacitance-loaded travelling-wave electrodes. We employ discrete multi-tone modulation controlled by a margin-adaptive bit-loading algorithm. In the experiment, the signal was transmitted over a 20-km dispersion-compensated single-mode fiber link and received by a single photodiode followed by a digital signal processor including a nonlinear equalizer. At a gross bit rate of 400 Gb/s, the bit error rate of the received signal was below the threshold of 20% overhead soft-decision forward error correction code. This result corresponds to a net data rate of 333 Gb/s.

A Novel Optical Frequency-Hopping Scheme Based on a Flexible Structure for Secure Optical Communications

A novel optical frequency-hopping scheme based on a flexible structure for secure optical communications is proposed and demonstrated. In the proposed scheme, critical users' data are divided into a lot of segments, and these segments are transmitted by different optical wavelengths in time domain. In other words, one channel optical carrier carries different users' data segments. A flexible structure was demonstrated and used in optical frequency-hopping system to simplify the structure and decrease the cost of the security system. In this paper, the viability of a four-wavelength-frequency-hopping secure optical communication system with a 25-Gb/s error-free transmission through a 32-km single-mode fiber and a 8-km dispersion compensation fiber was demonstrated and verified by simulation tools.

Transmission Performance Comparison of 16*100 Gbps Dense Wavelength Division Multiplexed Long Haul Optical Networks at Different Advance Modulation Formats under the Influence of Nonlinear Impairments

Abstract Higher spectral efficiency and data rate per channel are the most cost-effective approaches to meet the exponential demand of data traffic in optical fiber network communication system. In this paper, diverse modulation formats are analyzed for Dense Wavelength Division Multiplexed system at 100 Gbps * 16=1600 Gbps data rates. The performance analysis of proffered system for Non-Return to Zero, Return to Zero, Carrier- Suppressed Return to Zero and Duo binary RZ with duty cycle 0.5 to 0.7 ranges like modulation formats are considered to find optimum modulation format for a 100 Gbps bit rate per channel optical fiber transmission network system. The simulations are analyzed for different values of input power, length of fiber, nonlinear refractive index, nonlinear dispersion and nonlinear effective area for all above mentioned modulation formats with spacing 100 to 250 GHz. to evaluate the effect of modulation format Fiber Bragg Gratting, optical fiber amplifier and Dispersion Compensation Fiber dispersion compensation techniques are enacted on this proposed optical network system.

An Integrated High-Speed Full Duplex Coherent OFDM-PON and Visible-Light Communication System

Abstract We demonstrated a full duplex hybrid passive optical network and indoor optical wireless system employing coherent optical frequency division multiplexing. To accomplish reliable transmission in passive optical networks integrated visible-light communication (VLC), yellow light-emitting diode and infrared LED is used in downstream and upstream, respectively, for intra building network. In order to support high data rate, pulse-width reduction scheme based on dispersion compensation fiber is incorporated and system successfully covered the distance of 50 km. A data stream at the rate of 30 Gb/s is transmitted for each user out of eight users. VLC-supported users are catered with the bit rate of 1.87 Gb/s over 150 cm and in order to realize a low-cost system, visible and infrared LEDs are used in downlink and uplink, respectively.

Compensation of the Fluctuations of Differential Delay for Frequency Transfer in DWDM Networks.

This paper investigates the possibility of improving the stability of radio-frequency transfer in telecommunication dense wavelength division multiplexing fiber-optic networks. As it has been identified, the dispersion compensation fibers (DCFs), frequently used in these networks, cause substantial differential delay, whose temperature-induced fluctuations have the most significant impact on the deterioration of the stability of the frequency transfer. The authors present a method that allows achieving significant improvement in the long-term stability of the frequency transfer. The developed method is based on modeling the impact of DCFs with the help of remotely accessible temperature sensors factory installed by the manufactures in DCF modules. The effectiveness of the proposed solution has been tested on three different long-haul routes (up to 1550 km), set up in the operational Polish National Research and Education Network.

1.25 Gbits/s-message experimental transmission utilising chaos-based fibre-optic secure communications over 143 km

Chaotic optical secure communications (COSC) are a kind of fast-speed hardware encryption technique at the physical layer. Concerning the practical applications, high-speed long-haul message transmission is always the goal to pursue. In this paper, we report experimentally a scheme of long-haul COSC, where the bit rate reaches 1.25 Gbits/s and the transmission distance up to 143 km. Besides, a distinct advantage of low-cost is guaranteed with the off-the-shelf optical components, and no dispersion compensating fibre (DCF) or forward-error correction (FEC) is required. To the best of our knowledge, this is the first experimental evidence of the longest transmission distance in the COSC system. Our results show that high-quality chaotic synchronisation can be maintained both in time- and frequency-domain, even after 143 km transmission; the bandwidth of the transmitter is enlarged by the external optical injection, which leads to the realisation of 2.5 Gbits/s-message secure transmission up to 25 km. In addition, the effects of device parameters on the COSC are discussed for supplementary detail.

1.25 Gbits/s-message experimental transmission utilising chaos-based fibre-optic secure communications over 143 km

Chaotic optical secure communications (COSC) are a kind of fast-speed hardware encryption technique at the physical layer. Concerning the practical applications, high-speed long-haul message transmission is always the goal to pursue. In this paper, we report experimentally a scheme of long-haul COSC, where the bit rate reaches 1.25 Gbits/s and the transmission distance up to 143 km. Besides, a distinct advantage of low-cost is guaranteed with the off-the-shelf optical components, and no dispersion compensating fibre (DCF) or forward-error correction (FEC) is required. To the best of our knowledge, this is the first experimental evidence of the longest transmission distance in the COSC system. Our results show that high-quality chaotic synchronisation can be maintained both in time- and frequency-domain, even after 143 km transmission; the bandwidth of the transmitter is enlarged by the external optical injection, which leads to the realisation of 2.5 Gbits/s-message secure transmission up to 25 km. In addition, the effects of device parameters on the COSC are discussed for supplementary detail.

Designing Dispersion Flattened Photonic Crystal Fiber For Wideband Applications

In this paper, we proposed a dispersion flattened photonic crystal fiber (PCF) for having very low dispersion for wide bandwidth as well as low confinement loss. The proposed fiber has been numerically analyzed for Silica core as well as Borosilicate crown glass core with square lattice air holes. In the proposed design we have used elliptical air holes in the inner ring whereas outer rings are circular. Finite Element Method based software tool is used to analyze the proposed design. This comparison of core materials deduces that Borosilicate crown glass PCF produces negative dispersion, making it a good candidate to be used as Dispersion Compensating Fiber (DCF), whereas Silica PCF provides nearly zero dispersion at wavelength range 1.35 µm to 1.70 µm.

Optical Field Recovery in Stokes Space

Coherent detection empowers optical receivers the capability of recovering the optical field propagating through the fiber. Field recovery not only increases the degree of freedom for optical modulations, but also enables the digital compensation of fiber dispersion that avoids the sophisticated optical dispersion management. Compared with coherent detection, direct detection (DD) owns a natural advantage—the simplicity, but lacks the capability of field recovery. To increase the modulation dimension for DD, the recent development of Stokes vector receiver takes the advantage of polarization diversity and extends the modulation dimension up to three-dimension with reference to the four-dimensional coherent detection (i.e., dual-polarization intensity and phase). However, a Stokes vector receiver is not inherently capable of field recovery because the second-order signal representation in Stokes space nonlinearizes the first-order linear field information, making it infeasible to digitally compensate the chromatic dispersion. In this paper, we provide a comprehensive review of Stokes-space field recovery (SSFR) that completely or partially recovers the optical field by DD. We analyze the degree of freedom for a variety of Stokes-space modulations compatible with SSFR, and reveal their tradeoff between optical spectral efficiency (that determines fiber capacity) and electrical spectral efficiency (that determines transceiver cost per bit). We review the Stokes-space polarization recovery methods and generalize a novel concept as analog polarization identification to simplify the DSP of SSFR. Furthermore, we compare the OSNR sensitivity among various common direct detection schemes to provide reliable predictions of their transmission performance. With its high spectral efficiency and capability of digital dispersion compensation, SSFR is very promising for future high-capacity short-reach applications over single- or multispan fiber transmission.

All-fiber passively mode-locked laser using nonlinear multimode interference of step-index multimode fiber

We experimentally demonstrate for the first time, to the best of our knowledge, an all-fiber passively mode-locked laser operation based on the nonlinear multimode interference of step-index multimode fiber. Such a structure couples the light in and out of the multimode fiber via single-mode fibers, and its physical mechanisms for saturable absorption have been analyzed theoretically based on the third-order nonlinear Kerr effect of multimode fiber. Using the nonlinear multimode interference structure with 48.8 mm length step-index multimode fiber, the modulation depth has been measured to be ∼5%. The passively mode-locked laser output pulses have a central wavelength of 1596.66 nm, bandwidth of 2.18 nm, pulsewidth of ∼625 fs, and fundamental repetition rate of 8.726 MHz. Furthermore, the influence of total cavity dispersion on the optical spectrum, pulse width, and output power is investigated systematically by adding different lengths of single-mode fiber and dispersion compensation fiber in the laser cavity.

Enhanced Spectral Amplitude Coding OCDMA System Utilizing a Single Photodiode Detection

In this paper, the performance of a spectral amplitude coding-optical code division multiple access (SAC-OCDMA) system is investigated utilizing a single photodiode (SPD) detection technique. The proposed system uses enhanced double weight (EDW) codes as signature codes with three simultaneous users to overcome both phase-induced intensity noise (PIIN) and multiple access interference (MAI). In addition, a dispersion compensating fiber (DCF) is used in order to decrease the group velocity dispersion (GVD) caused in the single mode fiber. An erbium-doped fiber amplifier (EDFA) is used to overcome the attenuation. The use of both DCF and EDFA leads to an appreciable enhancement in the system performance. The system performance is evaluated through its bit error rate (BER), Q-factor, and received power. A comparison between the EDW codes and modified double weight (MDW) codes on the SAC-OCDMA system is demonstrated. Simulation is carried out through Optisystem ver. 7. The simulation results show that: (a) using an avalanche photodiode (APD) over PIN photodiode allows data transmission over longer distances; (b) the use of DCF improves the system BER;(c) using MDW codes gives better BER than using EDW codes.

20 Gb/s Hybrid CWDM/DWDM for Extended Reach Fiber to the Home Network Applications

Five channels hybrid DWDM/CWDM fiber to the home optical network with bit rate of 20 Gb/s has been demonstrated in this paper. The role of DWDM to increase the network capacity with the same service quality has been illustrated. Upgrading the already running network to cover the extra number of subscribers and the different destinations that asked for the fiber links is discussed. The role of the dispersion compensating fiber (DCF) in enhancing the network has been demonstrated. The comparison between the different methods of the dispersion compensation using DCF is illustrated. The effect of the DWDM on the network and optimizing the transmission power to achieve the required distances are discussed.

Temperature and Strain Discrimination in BOTDA Fiber Sensor by Utilizing Dispersion Compensating Fiber

Standard single mode fiber that normally used in Brillouin optical time domain analysis fiber sensors typically has only one Brilllouin gain peak (BGP), and its central frequency [i.e., Brillouin frequency shift (BFS)] can be affected by both temperature and strain, which gives rise to temperature and strain cross sensitivity. In this paper, we propose a new method to realize temperature and strain discrimination, for the first time to the best of our knowledge, by using commercial single mode dispersion compensating fiber (DCF) that has two BGPs located around 9.536 and 10.052 GHz, respectively. The two peaks have different temperature coefficients but nearly the same strain coefficients, which permits simultaneous temperature and strain sensing by combing the BFSs obtained from the two BGPs. The biggest advantage of the DCF is that the frequency space between its two BGPs is >100 MHz wider than some other fibers, ensuring much wider temperature and strain sensing range. In a proof of concept experiment, temperature and strain are fully discriminated with a temperature resolution of ~2.6 °C and a strain resolution of $\sim 64.6~\mu \varepsilon $ at the end of a 1-km sensing fiber with 2-m spatial resolution.

Long Reach and High Capacity Hybrid Passive Optical Network

<p>A number of applications are growing day by day and so the traffic. The need for bandwidth is also increasing at a rapid rate. The bandwidth and speed with which data can be transferred was very less when compared to core networks. The access network which was once a bottleneck is no longer so because of use of optic fiber (FTTH networks). A number of variants of Passive Optical Network (PON) have been proposed like the WDM PON and the Hybrid PON. Hybrid PON is a combination of TDM PON and WDM PON and is advantageous over WDMPON. This paper focuses on high capacity networks that can provide high data rate and long reach in the access part of the network. NRZ modulation format is normally used for transmission. We consider the advantages provided by the advanced modulation formats like DPSK. This modulation format is used to here and its benefits are evaluated in Hybrid PON network to increase the capacity and the reach of the network. Parameters like the BER and the Q factors are analysed using Optisystem Software. Distortion and the phenomena of dispersion can limit the performance of such a system. Hence Dispersion compensation mechanisms like the Dispersion Compensation Fiber (DCF) are used in the system to transmit data over large distance.</p>

An efficient way of third-order dispersion compensation for reshaping parabolic pulses through normal dispersion fiber amplifier

Normal dispersion decreasing fibers (NDDFs) employed for parabolic pulse (PP) generation are limited by the presence of inherent third-order dispersion (TOD), which leads to distortion in pulse shape from its parabolic nature. This necessitates a compensation method for TOD for such fibers. Dispersion-compensating fiber (DCF) amplifiers with relatively smaller values of dispersion can also be largely affected by this harmful effect of TOD when used for the same purpose. As a solution, a time-reversal system (TRS) based on a time-conjugating technique is employed with the aim of minimizing the deleterious effects of TOD. A detailed study on the estimation of the critical length where the time lens system needs to be implemented within the fiber link is crucial for reshaping the pulse into parabolic form. An NDDF is designed and optimized to possess a relatively higher value of TOD and a cascaded fiber optic system comprising the first stage of the proposed NDDF, the TRS and the second stage of the NDDF is suggested here to obtain linearly chirped PP at the output end even in the presence of a high value of TOD. The proposed scheme has also proved to be efficient for better pulse reshaping through DCFs possessing a high amount of TOD.