Extended Kalman filter (EKF) is a popular method to address the fast rotation of the state of polarization and large polarization mode dispersion in coherent optical communication. But it is usually underperforming in high-order modulation. Radius-directed idea is introduced to enhance the performance of EKF-based method. We call the proposed scheme radius-directed extended Kalman filter (RD-EKF). The performance of the proposed Kalman scheme is verified both in the polarization-division multiplexed 16QAM and 64QAM system. By the results, the RD-EKF scheme has better performance and less complexity than conventional EKF method in the high modulation format system.
A novel wired and wireless hybrid access system based on self-homodyne and heterodyne technology is presented in this paper. With the 16 Quadrature Amplitude Modulation(16QAM) and optimized self-homodyne mechanism, the system achieves 224Gbit/s wired access. Through optical heterodyne technology, the 30GHz wireless covering is implemented. The performance of the system is further improved by using the Pre-Compensation module and Post-Compensation module. Self-homodyne system improves the Optical Signal Noise Ratio(OSNR) threshold by 1.7 dB compared to the conventional coherent system, while reducing the system device requirements. The adoption of the Pre-Compensation module will save 1.7dB of OSNR tolerance even further. DSP modules of low computational complexity suitable for self-homodyne system and heterodyne system are redesigned.
KEYWORDS: Digital signal processing, Signal processing, Polarization, Analog to digital converters, Power consumption, Tunable filters, Signal filtering, Sampling rates, Optical engineering, Homodyne detection
Coherent optical communication critically relies on efficient digital signal processing (DSP). We demonstrate a lite DSP scheme to reduce the transmission cost and power consumption, which is mainly realized by reducing the sampling rate and simplifying the DSP algorithm. On the one hand, the baud-rate sampling technique based on the integral circuit can reduce the amount of data processing in DSP. On the other hand, we proposed a simplified joint modified constant modulus algorithm (MCMA) and phase-dependent decision-directed least mean square (DD-LMS) algorithm for adaptive blind polarization demultiplexing and phase recovery in which the butterfly structure is no longer needed for DD-LMS. And we compare the proposed simplified algorithm with the joint traditional CMA and blind phase search and the MCMA, in terms of performance in the 80-Gbaud dual-polarization 64QAM homodyne detection system. The results show that the proposed lite DSP mechanism can effectively reduce the power consumption of DSP by sub-rate sampling and simplifying the corresponding algorithm, which provides an alternative scheme for low-power optical interconnection of data centers.
KEYWORDS: Radio optics, Modulation, Radio over Fiber, Distortion, Transmitters, Singular optics, Single sideband modulation, Nonlinear optics, Heterodyning, Particle filters
We demonstrate a bidirectional radio-over-fiber system based on optical coupling sing-sideband modulation, which can effectively reduce the impact of nonlinear distortion in transmission. With sidebands heterodyne detection, the system achieves 60-GHz wireless coverage. By optical carrier reusing, the base station can omit the laser source to make the system colorless. Through simulation analysis, the system has the credible transmission property both in downlink and uplink transmissions.
A flexible optical filter based on tunable arrayed waveguide grating (AWG) with triangular-like model electrodes is designed on lithium niobate-on-insulator. Using the electro-optic effect of lithium niobate, the 10 − 3 increase of the waveguides refractive index could be achieved with a 4.348-V effective external voltage. The tunable range of the central wavelength of AWG can reach 3.8 nm and the 3-dB bandwidth is about 0.43 nm.
As the best candidate for wireless-access networks, radio-over-fiber (RoF) technology can carry a variety of business. It is necessary to provide differentiated services for different users, so the network needs to produce signals with different modulation formats and different frequencies. A reconfigurable RoF system based on a switch and tunable optical filter that can realize modulation format conversion and multiple frequency signal switching functions is designed. It has a good performance in terms of bit error rate and an eye diagram. The design can help to use radio frequency resources efficiently and make dynamic bandwidth resources controllable.
A phase-switch quadrature phase shift keying (PS-QPSK) modulation scheme is proposed for the radio-over-fiber (ROF) transmission system. In the downlink, the 60 GHz mm wave modulated by QPSK is generated by heterodyne detection. Systems implement compensation of chromatic dispersion with blind equalizations in the time domain and synchronization with the training sequence. The performance of the systems is evaluated in terms of constellation diagrams, bit error rate diagrams, and error vector magnitude. The effect of nonlinear crosstalk, in-phase/quadrature (IQ) mismatch of transmitter (Tx) and receiver (Rx) are taken into account in the performance evaluation. The PS-QPSK mechanism is analyzed comprehensively and systematically in an ROF system. In addition, the performance of the proposed system is compared to that of a traditional one adopting a phase-multiplexing quadrature phase shift keying (PM-QPSK) scheme. It reveals that the PS-QPSK-ROF system has a higher tolerance to nonlinear crosstalk and IQ mismatch than a PM-QPSK-ROF system.
A dmit2- salt: [(C4H9)4N]Au(dmit)2 was synthesized. Its third-order nonlinear optical properties of its acetone solution
were investigated by Z-scan technique using a pulsed laser with 28 ps duration and 10 Hz repetition at 532 nm. The
third-order nonlinear refractive index n2 and nonlinear absorption coefficient β of the sample solution were obtained to
be about 4.997×10-12 esu and 1.818 cm/GW at the concentration of 2×10-3 M. The second-order hyperpolarizability for
its molecular was estimated to be as large as 2.74×10-31 esu, suggesting [(C4H9)4N]Au(dmit)2 is a promising material for
all-optical switching.
KEYWORDS: Video, Fiber to the x, Internet, Interfaces, Digital signal processing, Network architectures, Wavelength division multiplexing, Modulation, Control systems, Networks
The paper proposes the design of Home Gateway used in FTTH. On the customer's
side, the Home Gateway finishes the optical signal receiving, provides three kinds of interfaces for
the video, voice data, and attains the integration of the three services. PAS6301 chip achieves the
control of voice, video and data services. Especially on the aspect of the video services, the HG
system combines the advantages of IPTV and the DVB to offer a platform for receiving two
signals. Users can use ordinary TV to receive both digital TV programs encoded by MPEG-2 and
IPTV programs encoded by H.264.
VoD is a very attractive service which used for entertainment, education and other purposes. In
this paper, we present an evolution method that integrates the EPON and SCM-PON by WDM
technology to provide high dedicated bandwidth for the metropolitan VoD services. Using DVB,
IPTV protocol, unicasting and broadcasting method to maximize the system throughput and by
numerical analysis, the hybrid PON system can implement the metropolitan VoD services.
Bismuth titanate, Bi4Ti3O12 (BTO), is a typical ferroelectric material with useful properties for optical memory,
piezoelectric and electro-optic devices. Its nano-crystals were compounded by the chemical solution decomposition
(CSD) technique. The structure and size of BTO were analyzed by X-ray diffraction (XRD) and transmissive electron
microscopy (TEM). Three sorts of composite films BTO/PEK-c with different BTO concentration were prepared by
spin-coating method at certain conditions. In this article, the scattering losses in thin films were obtained using the
photographic technique. The losses in the films with different BTO weight ratios were compared and analyzed.
A novel all-optical header and payload separation technique that can be utilized in unslotted optical packet switched networks is presented. The technique uses a modified terahertz optical asymmetric demultiplexer (TOAD) for packet header extraction with differential modulation scheme, and two semiconductor optical amplifiers (SOAs) that perform a simple XOR operation between the packet and its self-derived header to get the separated payload. The main virtue of this system is its simple structure and that it does not need any additional continuous pulses. Through numerical simulations, the operating characteristics of the scheme are illustrated. In addition, the parameters of the system are discussed and designed to optimize the operation performance.
We present a novel all-optical header and payload separation technique that can be utilized in Un-Slotted optical packet switched networks. The technique uses two modified TOADs, one is for
packet header extraction with differential modulation scheme and the other performs a simple XOR operation between the packet and its self-derived header to get the separated payload. The main virtue
of this system is simple structure and low power consumption. Through numerical simulations, the operating characteristics of the scheme are illustrated. In addition, the system parameters are
discussed and designed to optimize the performance of the proposed scheme.
In this paper, we present the model of switching matrix based on the XPM in SOA for optical packet-switched
networks, which is used to evaluate its performance. Cross-talk-induced bit error rate (BER), packet error rate (PER) and
cascadability under unbalanced traffic are examined, which proves to be relevant to the properties of signal pulse such as initial
chirp, shape and bit-rate. Several rules are drawn to facilitate the design of SOA-based switching matrix under unbalanced traffic.
A novel scheme of header extraction for optical packet switched networks is proposed for the first time. The system is based on a modified terahertz optical asymmetric demultiplexer (TOAD) with a differential modulation scheme. Numerical analysis and simulation show that more than 15-dB contrast ratio of the separated header at 2.5 Gbit/s to the suppressed payload at 40 Gbit/s can be achieved. In addition, the semiconductor optical amplifier (SOA) TOAD parameters are discussed and designed to optimize the performance of the proposed scheme.
The implementing of optical virtual private networks (OVPNs) over an optical burst-switching (OBS) network based on MPLS is discussed. The network architecture, the core and access nodes faculty are described. We also propose a new model with three traffic priorities, which used to analysis the delay and blocking performance of OVPN over OBS/MPLS network based on queuing theory.
A novel all-optical header and payload separation technique that can be utilized in un-slotted optical packet switched networks is presented. The technique uses a modified TOAD for packet header extraction with differential modulation scheme and two SOAs that perform a simple XOR operation between the packet and its self-derived header to get the separated payload. The main virtue of this system is simple structure and need not any additional continuous pulses. Through numerical simulations, the operating characteristics of the scheme are illustrated. In addition, the parameters of the system are discussed and designed to optimize the operation performance.
The use of optical buffering (OB) and wavelength converters (WC) is recognized as essential for reducing the complexity of optical packet switches (OPS). The object of this study is to investigate the performances of optical packet switches in which the wavelength converters are shared per input channel (SPIC) and optical buffering are partially shared working in unicast and multicast ways through analyzing a traffic model. We compare the packet loss probability of the unicast case and the multicast case, as the number of converters and depth of buffering in them are fixed. We also analysis of the improved performance by increase the number of wavelength in each channel.
Nonlinear Optical Loop Mirror (NOLM) is a very popular optical fiber device. When it’s inserted semiconductor optical amplifier (SOA), a lot of use it can be provided with. This work assesses the prospects for high-speed all optical wavelength conversion using semiconductor optical amplifiers inserted in NOLM based on cross-phase modulation (XPM) in a SOA and interference in Sagnac Interferometer. In this paper, we analyzed of parameters optimization for XPM wavelength conversion in the structure mentioned above, Segmented model for SOA, additional continuous control pulse are exploited in the theoretical analysis. The influence of an additional input light on converted waveform is shown. The output power and extinction ration changing with signal wavelength and input power are introduced.
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