Dispersion Compensation Device Research Articles

High-speed data transmission over a microresonator frequency comb with dispersion compensation for augmented data rates and reach

Abstract Microresonator frequency comb-based high-speed data transmission provides a pathway towards augmented data capacity without increasing the number of laser sources. Their use with intensity-modulated direct detection modulation (IMDD) formats is especially pertinent in data center communications where minimizing cost, latency and complexity is paramount. This however implies that the same extent of digital signal processing techniques commonly used in coherent detection for the management of fiber impairments including chromatic dispersion are not available. With the proliferation of silicon photonics technologies in data center transceivers integrated dispersion compensation which can overcome fiber impairments would be of great merit. We demonstrate low power generation of the primary comb state in a silicon nitride microresonator and transmission of 25 Gb/s NRZ and 50 Gb/s PAM4 data over 20 km of single mode fiber. This represents the longest fiber reach demonstrated to date for the transmission of IMDD data using an integrated, microresonator frequency comb. An integrated, tunable grating device for dispersion compensation that reduces dispersion impairments after several fiber lengths generates significant improvements in the eye diagram, six orders of magnitude improvement in the bit-error rate and 14 dB improvement in the transmitter and dispersion eye closure quaternary values. Concurrently, doubling data transmission is demonstrated via polarization multiplexing a comb line and successful dispersion compensation of up to 20 km.

Slow‐Light‐Based Dispersion Compensation of High‐Speed Data on a Silicon Nitride Chip

Transmission of optical data over fiber is subjected to signal degradation from dispersion impairments that worsen with increasing fiber lengths and higher data rates. Consequently, dispersion impairments significantly limit the data rates and reaches of transceivers used for data center communications. Herein, the design and experimental demonstration of a low loss, CMOS‐compatible on‐chip silicon nitride transmission grating device for dispersion compensation of high‐speed data are reported. The design, which involves inscribing a perturbation in the effective index profile of the grating, generates a considerable increase in the dispersion magnitude and enables up to 25 km of single‐mode fiber to be compensated for. Importantly, high‐speed measurements after dispersion compensation of a 20 km single‐mode fiber, using non‐return‐to‐zero data at rates up to 28.05 Gb s−1 show nine orders of magnitude reduction in BERs from 5 10−1 to 1 10−10, accompanied by significant improvements in the eye diagram. The underlying operating mechanism involves slow‐light effects that are designed to generate large dispersion while maintaining low losses. A pathway toward dispersion impairment‐free high‐speed data transmission over fiber using a compact device is demonstrated, which can be seamlessly integrated within transceiver chips, bringing the applicability of slow‐light devices firmly into the domain of commercial viability.

90-fs Yb-doped fiber laser using Gires-Tournois interferometers as dispersion compensation

This paper reports a Yb-doped mode-locked femtosecond fiber laser based on a nonlinear amplifying loop mirror (NALM). The improved NALM structure ensures the high repetition rate of 97 MHz and the maximum output power of 126 mW. The Gires-Tournois interferometers (GTI) are used as dispersion compensation devices in laser resonator. The pulse output with full width half maximum (FWHM) of 26 nm and a dechirped pulse duration of 90 fs is obtained. As far as we know, this is the relatively short pulse in an improved NALM mode-locked Yb-doped fiber laser.

Dispersion compensation of high-speed data using an integrated silicon nitride ring resonator.

Dispersion impairments are a well-known limitation in data center communications, limiting both the usable data rates and reaches. Several companies today adopt silicon photonics as a core technology in their transceiver products. This presents an opportunity for silicon photonics-based dispersion management technologies to be integrated with the transceiver transmitter or receiver. In this manuscript, we present a ring-resonator based, tunable dispersion compensation device, providing dispersion ranging as wide from + 12.9 × 103ps/nm to -12.3 × 103ps/nm. Thermo-optic tuning from 20°C to 70°C is demonstrated to allow continuous wavelength tuning across 200 GHz. High-speed experiments using 25 Gb/s non-return-to-zero data propagating through 20 km of single mode fiber show that a significant improvement in the eye diagram is achieved after compensation with the ring-resonator device. We demonstrate a significant improvement in the BER from 10-3 to 10-11 for data rates of 25 and 25.78125 Gb/s.

Suppression of Frequency Modulation to Amplitude Modulation Conversion with Modified Group Velocity Dispersion Compensation Device in the Front End of High-Power Lasers

The group velocity dispersion (GVD) occurring in the front end of high-power lasers is one of the primary factors leading to the conversion of frequency modulation (FM) to amplitude modulation (AM). In this paper, we propose a modified, active, closed-loop feedback compensation device for GVD-induced FM–AM conversion, using a two-dimensional, electric, adjustable mirror mount and parallel grating pair to improve the long-term stability, efficiency of adjustment, and accuracy of compensation. Experimental results of a 12 h FM–AM depth test revealed that the depth varied between 2.28% and 5.22%. Moreover, we formulated a mathematical relationship between the dispersion parameters and temperature in optical fibers to analyze the intrinsic effect of temperature on FM–AM. The related simulation and experimental results consistently validated the quantitative relationship between the temperature and FM–AM depth.

Design and analysis of high birefringence and nonlinearity with small confinement loss photonic crystal fiber

High birefringence with low confinement loss photonic crystal fiber (PCF) has significant advantages in the field of sensing, dispersion compensation devices, nonlinear applications, and polarization filter. In this report, two different models of PCFs are presented and compared. Both the models contain five air holes rings with combination of circular and elliptical air holes arrangement. Moreover, the elliptical shaped air holes polarization and the third ring air holes rotational angle are varied. To examine different guiding characteristics, finite element method (FEM) with perfectly matched layer (PML) absorbing boundary condition is applied from 1.2 to 1.8 μm wavelength range. High birefringence, low confinement loss, high nonlinearity, and moderate dispersion values are successfully achieved in both the PCFs models. Numeric analysis shows that model-1 gives higher birefringence (2.75 × 10–2) and negative dispersion (–540.67 ps/(nm$km)) at 1.55 μm wavelength. However, model-2 gives more small confinement loss than model-1 at the same wavelength. In addition, the proposed design demonstrates the variation of rotation angle has great impact to enhance guiding properties especially the birefringence.

40 Gb/s DWDM Structure with Optical Phase Configuration for Long-Haul Transmission System

AbstractWe propose the experimental transport of 48 channels with 40 Gbit/s dense wavelength-division multiplexing (DWDM) system that uses single-mode fiber (SMF) in combination with dispersion compensation fiber (DCF) which is a dispersion compensation device, in C and L band wavelength range to solve the dispersion program. The DWDM system scheme employing single Mach–Zehnder modulation (MZM) return-to-zero differential phase-shift keying (RZ-DPSK) modulation format with hybrid Raman/EDFA (Erbium-doped fiber amplifier) configuration to improve transmission signal, and employing an optical phase conjugation (OPC) configuration in the middle line. That can compensate for dispersion impairment and improve nonlinear effects to investigate transmission distance performances.

DWDM Transmission with LEAF and RDF Structure in 40 Gb/s Single MZM with RZ-DPSK Modulation

AbstractWe propose the experiment transport of 48 Chs 40 Gb/s dense wavelength division multiplexing (DWDM) system that uses larger effective area fiber (LEAF) in combination with reverse dispersion fiber (RDF), which is a dispersion compensation device, in C band (1,530–1,560 nm) and L band (1,570–1,610 nm) wavelength range to solve the dispersion program. The single Mach–Zehnder modulation (MZM) format with erbium-doped fiber amplifier (EDFA) configuration to generate return-to-zero differential phase-shift keying (RZ-DPSK) modulation signal can compensate dispersion impairment in 48×40 Gb/s DWDM system. The proposed 48×40 Gb/s DWDM system successfully employs single MZM RZ-DPSK modulation format to reduce modulation complex configuration with EDFA to promote the power signal and using LEAF and RDF in 28 spans over 3,360 km ultra-long-haul fiber transmission successfully.

Modified decoding and detection scheme for spectral amplitude coding optical CDMA systems

In this reported work, a modified decoding and detection scheme with dispersion compensation is investigated for spectral-amplitude-coding optical code division multiple access (SAC-OCDMA) systems. For simultaneously decoding and compensating the chromatic dispersion of signals in the 40 km-long standard single-mode fibre transmission, based on reconstruction equivalent-chirp method the array configuration of fibre Bragg grating (FBG) segments can be controlled with a quadratic dispersion of −680 ps/nm for an extra time delay. The traditional triple-branch signal detection (TBSD) scheme is then modified and the principle of multiuser interference elimination is theoretically analysed. The simulated results show that, without adding a dispersion compensation device, the modified TBSD scheme adopting the FBG decoder can realise the decoding and detection function in SAC-OCDMA.

Designing an Ultra-Negative Dispersion Photonic Crystal Fiber with Square-Lattice Geometry

We have theoretically investigated the dispersion characteristics of dual-core PCF, based on square-lattice geometry by varying different parameters. The fiber exhibits a very large negative dispersion because of rapid slope change of the refractive indices at the coupling wavelength between the inner core and outer core. The dependence of different geometrical parameters, namely, hole-to-hole spacing (Λ) and different air-hole diameter (d), was investigated in detail. By proper adjustment of the available parameters, a high negative dispersion value of -47,500 ps/nm/km has been achieved around the wavelength of 1550 nm. Our proposed fiber will be an excellent device for dispersion compensation in long-haul data transmission as being thousand times more than the available DCFs.

Ultrafast laser performance of Yb 3 + : Sc 2SiO 5 crystal with a single-walled carbon nanotube absorber

Single-walled carbon nanotube (SWCNT) absorber fabricated by vertical evaporation is used in passively mode-locked Yb 3 + :Sc 2SiO 5 (Yb:SSO) ultrafast laser for the first time. The performance of Yb:SSO ultrafast laser with pulse width as short as 880 fs is studied and the average output power is 712 mW. To our knowledge, this is the highest output power of femtosecond lasers with SWCNT-SAs reported. In addition, we firstly demonstrate a passively mode-locked picosecond Yb:SSO laser without inserting any dispersion compensation device. The pulses width is as short as 5.4 ps and the output power is 940 mW.

Improving the privacy of optical steganography with temporal phase masks

Temporal phase modulation of spread stealth signals is proposed and demonstrated to improve optical steganography transmission privacy. After phase modulation, the temporally spread stealth signal has a more complex spectral-phase-temporal relationship, such that the original temporal profile cannot be restored when only dispersion compensation is applied to the temporally spread stealth signals. Therefore, it increases the difficulty for the eavesdropper to detect and intercept the stealth channel that is hidden under a public transmission, even with a correct dispersion compensation device. The experimental results demonstrate the feasibility of this approach and display insignificant degradation in transmission performance, compared to the conventional stealth transmission without temporal phase modulation. The proposed system can also work without a clock transmission for signal synchronization. Our analysis and simulation results show that it is difficult for the adversary to detect the existence of the stealth transmission, or find the correct phase mask to recover the stealth signals.

Automatic Chromatic Dispersion Compensation Method Based on Spectrum Change of Transmission Signal

Because of increase of communication bandwidth demand, upgrading the speed of optical fiber networks is a future issue. However, in the case of high speed transmission at wavelength of 1.5 μm band on the existing single mode fiber, transmission distance is limited due to chromatic dispersion. Thus, in addition to chromatic dispersion compensation devices, automatic optimization methods of the compensation value are important especially in the case of photonic networks, on which transmission distances often change dynamically. But problems remain such that signal quality measuring instruments are expensive under existing automatic chromatic dispersion compensation methods.In this report, focusing on spectrum profile change by long transmission of optical signals, a simple automatic control method of chromatic dispersion compensation is proposed. And some results of basic experiments are described. By doing feedback control for optimizing the chromatic dispersion compensation value, an error-free state of a 10 Gbps optical signal is demonstrated even if the dispersion value of the transmission line is rapidly changed.

Transmission 32 × 10 Gb/s using LEAF and RDF in C band and L band for DWDM dispersion compensation

AbstractWe propose the experiment transport of 32 channels 10 Gbit/s dense wavelength division multiplexing (DWDM) system which uses large effective area fiber (LEAF) in combination with reverse dispersion fiber (RDF), which is a dispersion compensation device, in C and L band wavelength range to solve the dispersion program. The system structure transmission length of 800‐km consisted of 75‐km LEAF and 5‐km RDF for ten fiber spans. Q factor should be greater than 6 dB for good performance, corresponding to a bit error rate (BER) of less than 10−9, and all 32 channels have been measured for both Q factor and BER. The proposed system is applicable for ultra long‐haul transmission in DWDM systems. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2489–2492, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24667

Polarization dynamics in optical ground wire network

We report the polarization dynamics in an optical ground wire (OPGW) network for a summer period and a fall period for what is believed to be the first time. To better observe the surrounding magnetic fields contribution to modulating the state of polarization (SOP) we installed a Faraday rotating mirror to correct reciprocal birefringence from quasi-static changes. We also monitored the OPGW while no electrical current was present in the towers' electrical conductors. The spectral analysis, the arc length mapped out over a given time interval on a Poincaré sphere, histograms of the arc length, and the SOP autocorrelation function are calculated to analyze the SOP changes. Ambient temperature changes, wind, Sun-induced temperature gradients, and electrical current all have a significant impact on the SOP drift in an OPGW network. Wind-generated cable oscillations and Sun-induced temperature gradients are shown to be the dominant slow SOP modulations, while Aeolian vibrations and electrical current are shown to be the dominant fast SOP modulations. The spectral analysis revealed that the electrical current gives the fastest SOP modulation to be 300 Hz for the sampling frequency of 1 KHz. This has set the upper speed limit for real-time polarization mode dispersion compensation devices.

Virtual Gires-Tournois etalons realized with phase-modulated wideband chirped fiber gratings

We propose and demonstrate novel virtual Gires-Tournois (GT) etalons based on fiber gratings. By introducing an additional phase modulation in wideband linearly chirped fiber Bragg gratings, we have successfully generated GT resonance with only one grating. This technique can simplify the fabrication procedure while retaining the normal advantages of distributed etalons, including their full compatibility with optical fiber, low insertion loss, and low cost. Such etalons can be used as dispersion compensation devices in optical transmission systems.

Spectra profile expansion of Bragg wavelength on nano-particle embedded fiber-Bragg-grating

This article presents the results of a detailed study on the effects of spectra profile expansion of Bragg wavelength on the performance of the nano-particle embedded fiber-Bragg-grating (nano-EFBG) for sensing applications. The fiber-Bragg- grating (FBG) was coated by CdSe-nano-particle layers with various thicknesses (600–2000 nm) and bonded on substrates of epoxy or epoxy/Teflon with a large thermal expansion coefficient. With this embedding method, a variation of the line-width expansion of Bragg wavelength with cooling down FBG has been controlled. The nano-EFBG morphology was investigated by FE-SEM and the nano-EFBG sensors are studied in ambient from 77 K (liquid nitrogen) to 393 K. The expansion of spectral profile, which caused by transverse loading from nano-particle/epoxy layers, can be changed in the range of 0.1–1.3 nm between before and after cooling down. This result is for the strain-temperature sensors, but has the potential application in the FBG dispersion compensation devices and many other measurands.

Employing photonic crystal fiber to improve composite second-order and composite triple-beat performances in a two-wavelength wavelength-division-multiplexing transport system

A two-wavelength wavelength-division-multiplexing (WDM) externally modulated transport system employing photonic crystal fiber (PCF) as a dispersion compensation device to compensate the fiber dispersion and to reduce the cross-phase modulation (XPM)–induced cross talk is proposed and demonstrated. In comparison with a two-wavelength WDM externally modulated transport system without a dispersion compensation device or with a conventional dispersion compensating fiber (DCF) as a dispersion compensation device, good performances of composite second-order (CSO) and composite triple beat (CTB) were obtained accompanied by acceptable carrier-to-noise ratio (CNR) in our proposed system.

Importance of Intrinsic-$Q$ in Microring-Based Optical Filters and Dispersion-Compensation Devices

We investigate the impact of the intrinsic-Q of the resonant poles on the performance of multiring-based optical filters and dispersion-compensating devices. We highlight the role of quality factor by defining figures-of-merit for some specific filter configurations.

The system of L-band 2 × 10 Gb/s WDM transmission over conventional single mode fibre with 600 km by chirped fibre Bragg gratings dispersion compensation

A chirped fibre Bragg grating according to ITU-T suggested L-band (2nd channel λ1 = 1570.83 nm; 80th channel λ2 = 1603.57 nm) with more than 1800 ps/nm single channel dispersion compensation is presented in this paper, of which the cladding mode loss, the delay curve ripple and the power fluctuation of the reflected spectrum are less than 0.5 dB, 50 ps and 0.25 dB, respectively. With this new FBG as dispersion compensation device, a 2 × 10 Gb/s wavelength division multiplexing (WDM) L-band transmission of 600 km based on conventional single mode fibre (G.652 fibre) is performed without forward error correction. The bit error rate (BER) is less than 10−12 and the power penalties of the 2nd and 80th channel of L-band are 1.8 dB and 2.0 dB, respectively.