KEYWORDS: Computing systems, Passive optical networks, Network architectures, Optical engineering, Reliability, Time division multiplexing, Field programmable gate arrays, Telecommunications, Data transmission, Control systems
A passive optical network (PON) based real-time Ethernet (PONRTE), which can take advantage of PON features such as broad bandwidth, high reliability, and easy maintenance to satisfy the determination and real-time requirements of high performance industrial applications, is proposed. The protocol model and network architecture having a compatible physical layer and MAC layer with Ethernet passive optical network are presented for the proposed PONRTE. A fixed periodic time slot allocation mechanism including a synchronic time division multiplexing transmission and an asynchronic data transmission is adopted to guarantee the determination and real-time of the communication. A simple and easy to implement time synchronization approach, where the starting time of the first transmission slot of an access node is synchronized by a relative time synchronization while the starting time of subsequent slots is determined by the fixed period and a dynamic time synchronization, is designed to support the fixed time slot allocation mechanism and avoid the collision in PONRTE. A 100 Mb/s PONRTE experimental testbed with 16 access nodes and a time allocation period of 240 μs is demonstrated. The results show that the experimental PONRTE can work stably and reliably with a frame loss ratio less than 10 −7 .
To improve the reliability and scalability that are very important for large-scale all optical fiber sensor networks
(AOFSN), three-level hierarchical sensor network architectures are proposed. The first two levels consist of active
interrogation and RNs, respectively. The third level called sensor subnet (SSN) consists of passive FBGs and a few
switches. As AOFSN is mainly multiplexed by wired and passive FBGs, the routing algorithm for scanning sensors is
determined by the virtual topology of SSN due to the passivity. Therefore, the research concentrates on the construction
of SSN and aims at proposing regular and unicursal virtual topology to realize reliable and scalable routing schemes.
Two regular types of SSNs are proposed. Each type consists of several sensor cells (SC), square-based SC (SSC) or
pentagon-based SC (PSC) and is scaled several times from the SCs. The virtual topologies maintain the self-similar
square- or pentagon-like architecture so as to gain simple routing. Finally, the switch architecture of RN is proposed for
the reliability of the first two levels; and then, the reliability and scalability of SSN are discussed in view of how much
link failures can be tolerant, and how each SC is scaled to maintain the self-similarity, respectively.
In this paper, we propose a novel compound high order microring resonator all-pass filter by employing an assistant microring between two cascaded microrings. It improves the dispersion compensation ability and provides a wide bandwidth. The extension of group delay range is shown in its group delay response, which allows flexible choice of the microring size for technical convenience and bend loss improvement. The careful design of coupling coefficients is able to optimize the group delay response.
A novel configuration for the transducer of magnetostrictive fiber-optic sensors was proposed and implemented. It is composed of a rectangle and two half-circles. The transducer with the novel configuration has not only higher sensitivity than that of traditional configurations, but good directivity. The magnetostriction was analyzed compared with that of cylindrical transducers. It is shown that the system sensitivity can be improved by increasing the long-side of rectangle and shortening the perimeters of the two half-circles.
Two transducers with cylindrical and racetrack configurations were fabricated. Moreover, an experimental setup to measure the low-intensity magnetic field detection responses was built up. Experimental results verified the analysis.
For its good directivity, three of them can be compounded as a vector magnetometer to measure three orthogonal components of magnetic field.
In this paper, a kind of tunable wavelength selective optical switch was proposed with two-input/two-output fiber ports. It is based on tunable Fabry-Perot cavity by a pair of multi-layered piezoelectric ceramics. Each fiber carries N wavelengths, one of which can be selected. The tunable span can reach 5.43 nm under 10 V DC voltages. The relation of wavelength tuning ability and driving voltage is linear. The maximum of difference between theoretical and experimental results is less than 0.08nm. The quantities of maximum insertion loss, switching time and on/off ratio are about 3 dB, 1 ms and 28 dB
Optical burst switching (OBS) is more efficient and feasible solution to build terabit IP-over-WDM optical network by employing relatively matured photonic and opto-electronic devices and combining the advantage of high bandwidth of optical transmission/switching and high flexibility of electronic control/processing. Channel scheduling algorithm is one of the key issues related to OBS networks. In this paper, a class-based scheduling algorithm is presented with emphasis on fairly utilizing the bandwidth among different services. A maximum reserved channel numbers and a maximum channel search times is introduced for each service based on its class of services, load and available bandwidth resource in the class-based scheduling algorithm. The performance of the scheduling algorithm is studied in detail by simulation. The results show that the scheduling algorithm can allocate the bandwidth more fairly among different services and the total burst loss ratio under high throughput can be lowered with acceptable expense on delay performance of services with lower delay requirement. Problems related with burst loss ratio and the delay requirement of different services can be well solved simultaneously.
Optical burst switching (OBS) has been emerging as a promising technology that can effectively support the next generation IP-oriented transportation networks. JIT signaling protocol for OBS is relatively simple and easy to be implemented by hardware. This paper presented an effective scheme to implement the JIT protocol, which not only can effectively implement reservation and release of optical channels based on JIT, but also can process the failure of channel reservation and release due to loss of burst control packets. The scheme includes: (1) a BHP (burst head packet) path table is designed and built at each OBS node. It is used to guarantee the corresponding burst control packet, i.e. BHP, BEP (burst end packet) and BEP_ACK (BEP acknowledgement), to be transmitted in the same path. (2) The timed retransmission of BEP and the reversed deletion of the item in BHP path tables triggered by the corresponding BEP_ACK are combined to solve the problems caused by the loss of the signaling messages in channel reservation and release process. (3) Burst head packets and BEP_ACK are transmitted using “best-effort” method. Related signaling messages and their formats for the proposed scheme are also given.
The first optical burst switching (OBS) system has been demonstrated in China, which includes three edge routers and one core-node. A kind of fast wavelength selective optical switching was used in the system. The core OBS node consists of a kind of wavelength selective optical switch we developed. It consists of two SOA switches and one wavelength selective thin film filter with centre wavelength at one wavelength. There are one input optical fiber and two output fibers, each fiber carries two wavelengths. The Dell PE2650 servers act as the edge OBS routers. The wavelength of each data channel is located in C-band and the bit rate is at 1.25Gbps. The control channel uses bit rate of 100Mbps at wavelength of 1310 nm. A novel effective scheme for Just-In-Time (JIT) protocol was proposed and implemented. OBS services, such as Video on Demand (VOD) and file transfer protocol (FTP), have been demonstrated. Assembling and scheduling methods that are capable to guarantee the QoS (quality of service) of the transported service are studied.
It is proposed and demonstrated that the fiber-optic Mach-Zehnder (MZ) interferometry can measure accurately the elector-optic (EO) coefficients of, not only the polymer thin film, but also the polymer waveguide. Furthermore, the tensor components, both r<sub>13</sub> and r<sub>33</sub>, of the EO coefficient can be measured simultaneously. In contrast with the free space MZ interferometer, the fiber-optic MZ interferometer owns some advantages, such as fewer devices, simple experiment configuration, easy operation, and good stability. The most outstanding advantage is that the second electrode need not be fabricated on the top of the polymer thin film. So, the measurement system is especially
suitable to measure E-O coefficients of the polymer samples on trial. The closed loop control system of the phase bias of the MZ interferometer decreases the requirement of the environment stability and increases the measurement precision.
A novel fast tunable electro-optic (EO) polymer waveguide grating is proposed and designed. Its resonant wavelength can be linearly tuned by first-order EO effect with a high sensitivity of 6.1pm/V. Its spectrum characteristics depend strongly on many grating parameters, such as refractive index modulation, modulation function, grating period and period number. Material selection, fabrication technology, EO tuning ability and polarization dependence of EO polymer waveguide grating are also discussed. This waveguide grating not only overcomes the shortages of optic fiber gratings, such as slow wavelength tuning ability, and large-scale integration inconveniency, but has many advantages, such as high resonant wavelength tune sensitivity, same fabrication technology as semiconductor, and polarization independence.
In this paper, a novel semi-analytical algorithm for calculating backward-pumped Raman amplifier is proposed. The algorithm does not need iteration and can greatly save the computational time. Simulation results for Raman amplifiers with 25 km and 50 km fibers show that the accuracy of the method is quite satisfying in comparison with the shooting algorithm and the deviation is within 0.02 dB.
A novel configuration of semiconductor all-optical switch based on Fabry-Perot cavity is proposed. The principle and
structure of this kind of all-optical switch are presented. We also analyze the performance of the all-optical switch. The
wavelength selectivity of the all-optical switch changed with the power of the control light is given. We discuss its
viable application in the future optical switching.
Optical burst switching (OBS) is a promising solution for realizing IP over WDM since it combines the advantages of optical circuit switching and optical packet switching (OPS) while overcoming their shortages. In this paper, the mechanisms to implement burst assembly and scheduling in an OBS edge router are discussed. The performance of the output traffic from the edge router, e.g. traffic shape and delay, is analyzed with simulation results. The results show that the traffic shape and the delay are affected by maximum delay specified by different classes of services, the maximum length of the burst, the burstiness of the traffic, and the mechanisms of burst assembly and scheduling. By properly designing, the traffic shape can be improvement while the delay keeping in the bounds.
Optical Burst Switching (OBS) functioning as an IP traffic aggregator at the edge of the Optical Transport Network is provided to enhance network flexibility and efficiency. This paper gives an overview of OBS node and the benefits it will bring about. It explains how an OBS node is modeled and simulated under different traffic conditions and gives the effect of Fiber Delay Line (FDL) in OBS node. Finally, the simulation results are presented and the performances of OBS node are evaluated.
In this paper, the process of fabricating coarse wavelength division multiplexing (CWDM) passive components using Fused Biconic Taper (FBT) technology is introduced. The performances and specifications of CWDM passive components are measured and reported. And we compare the performances and cost of this kind of CWDM module with the performances and cost of CWDM module based on thin-film-filter technology and dense wavelength division multiplexing (DWDM) module.
In this paper, we propose an optical switch that combines both shared tunable wavelength converter and partially shared buffering together. The packet contention can be resolved both in the time domain (output buffering and partially shared buffering) and frequency domain (wavelength conversion) simultaneously and switching performance can be greatly improved. Various simulations are carried out to show the performance of different buffering and wavelength conversion structures. The results confirm that the switching architecture we proposed has excellent performance.
Optical fiber Raman amplifiers are well suited for application in optical DWDM systems and networks. Instantaneous pump depletion due to different pump power requirement of bit 1's and bit 0's will induce extra optical noise and cross talk. This paper analyzes this kind ofnoise source and presents simulation results of the dependence of optical SNR drop on fiber length, bit rates and channel numbers.
Broad band-rejection all fiber filters based on Long Period Fiber Gratings were fabricated by a novel method. Adopting the grating period (Lambda) equals 550 micrometer, and (Lambda) equals 610 micrometer, number of periods N equals 15 and different heating condition, the two kinds of devices are obtained with different band-rejection peak wavelengths at 1310 nm and 1550 nm, respectively. The isolation is more than 25 dB. The bandwidth at the 10 nm isolation point is over 20 nm. The insertion loss is less than 1.2 dB and backward reflection loss is less than -70 dB.
In this paper, we improve the rate equations of the Single Quantum Well Laser Diodes (SWQ-LD's) by introducing photon phase equation and three terms of Langivin noise for carriers and photons. Modeling of SQW-LD by means of Matlab Simulink is present. Small signal modulation response, relative intensity noise (RIN) and phase noise are studied. Various simulation results are given.