Multi-channel arrayed waveguide devices are crucial for WDM optical communication systems. Multi-channel arrayed polymer-based waveguide devices have been important for reducing cost and size. This paper introduces two types of multi-channel arrayed polymer-based waveguide devices. We designed and fabricated a four-channel arrayed 22 thermo-optic switch using a low-loss polymer and a four-channel arrayed electro-optic Mach-Zehnder modulator using an electro-optic polymer. The four-channel arrayed 22 thermo-optic switch has very low power consumption and uniform performance. The switching time of the four-channel arrayed EO Mach-Zehnder modulator operating with just lumped electrodes is less than a few nanoseconds.

In wavelength division multiplexed networks, shared path protection provides the same level of protection against a single fiber-link failure as dedicated path protection with potentially higher network utilization. The shared path protection is more complex to provision and maintain. In this paper, we introduce a parameter, the degree of sharing, which refers to the number of protection paths that a wavelength can be assigned to on a link. We propose methods for calculating the maximum degree of sharing. We consider on-line routing and wavelength assignment (RWA) of protection paths that are established for incremental traffic using the maximum degree of sharing. Establishment of protection paths using the maximum degree of sharing can simplify the algorithm. We compare the results on the decreased calculation time with accepted connection requests for a given number of wavelengths, assuming that wavelengths are assigned according to the First-Fit policy for working paths and Last-Fit policy for protection paths. The more wavelengths are used, the more calculation time can be reduced. When the load increases, the decreasing rate of calculation time also increases.

A simple nation-wide core network architecture based on the optimized combination of WDM and OTDM technologies in a two-tier structure network is proposed. The dynamic timeslot allocation in a fixed length frame structure associated with the wavelength routing scheme creates a virtual path with variable bandwidth for edge-to-edge transport of any type of packet protocol without O-E-O conversion. The simulation results show that dynamic timeslot assignment with bandwidth reservation is the best alternative for the network bandwidth utilization efficiency. The influence of the delay caused by the physical size of the network during the request-acknowledgement process is also discussed.

We clarify the effectiveness of receiver-side compensation in offsetting fiber Bragg grating (FBG) dispersion induced-electrical signal-to-noise ratio (SNR) degradation in a 10 Gb/s 8-channel wavelength-division multiplexing (WDM) 6,400 km transmission system. The receiver-side compensation greatly improves the SNR degradation. The allowable accumulated FBG dispersion is -400 1000ps/nm for the worst arrangement, a single FBG at the transmitter, which is about half the accumulated fiber dispersion permissible with receiver-side compensation.

This paper presents a comprehensive investigation of three optical wavelength-division multiplexed (WDM) mesh network protection approaches, namely minimal cost, single link basis and disjoint path approaches. The operation of each approach is described and their performances are extensively evaluated and compared. Key aspects that are taken into the consideration and comparison of the designs include a spare capacity requirement, ease of operation and practical feasibility. A mathematical model based on integer linear programming is introduced to obtain a lower bound on the spare capacity requirement for full protection against all single link failures. Two heuristic algorithms have also been developed to perform wavelength resource allocation under both normal and failure conditions for both systems with and without wavelength conversion capability. It is shown that the minimal cost approach can accomplish the lowest extra cost requirement for protection, but this approach is considered not appropriate for practical applications due to complicated restoration and management. The single link basis scheme is on the other hand more practical and very cost efficient. For the disjoint path technique, the cost for spare capacity is generally slightly greater than that of the single link basis scheme. Its main advantages lie in the simple re-configuration and inherent protection against node failure for in-transit traffic. Finally, a new framework for obtaining a good spare capacity cost estimate of a mesh restorable network is presented.

Using less wavelengths to serve more communication channels is one of the primary goals in the design of WDM networks. By installing wavelength converters at some nodes in a network, the number of wavelengths needed can be reduced. It has been observed that the more converters installed in a network, the less number of wavelengths is needed, given the same network load. In this paper, we study the relationship between the number of converters and the number of wavelengths needed in a system, and propose a suite of theories and results on how to place the minimal number of converters in the system so that the number of wavelengths W is at most a constant α times the maximal link load L (i.e., W α L), where α = 3/2 or 5/3. The results show a significant saving of converters in networks of both special topologies and general topology.

This paper proposes an asymmetric bandwidth access network based on super-dense wavelength-division multiplexing (SD-WDM) technologies; the network guarantees 100 Mbps upstream and 1 Gbps downstream bandwidth to each user and supports wide-area transmission. The network minimizes operation and administration costs by consolidating switching equipment, as well as minimizing wavelength monitoring/stabilization functions by employing two technologies; the optical multi-carrier supply module (OCSM) for creating downstream signals and the directly modulated spectrum slicing scheme for creating upstream signals. After describing the configuration and features of the presented network, we demonstrate a bandwidth guaranteed network for each of 64 users with 100 Mbps upstream and 1 Gbps downstream bandwidth. The network provides 10-km access lines with under 7-dB loss from users to the access node and a 120-km metro-loop transmission line with under 25-dB loss from the access node to the center node.

We have developed an experimental 5-Tb/s packet-by-packet wavelength switching system, OPTIMA-2. This paper describes its hardware architecture. OPTIMA-2 is a non-blocking 3-stage switch using optical wavelength division multiplexing (WDM) links and dynamic bandwidth-sharing. A new scheduling algorithm for variable-length packets is used for the receiver ports of WDM links and simulation results show that it can suppress short-packet delay while keeping high throughput. An implementation of the WDM link using field programable gate arrays and a compact planar lightwave circuit platform is described. Experimental results for the basic operation of optical wavelength switching are also presented.

Wavelength division multiplexed (WDM) routed optical networks represent the direction towards future high-capacity wide-area network applications. A serious issue in WDM-routed networks, though, is light-path allocation which requires a combination of optical routing and wavelength assignment. While near-optimal-routing and wavelength-assignment algorithms aimed at minimizing network wavelength requirements have been reported, the practicability of wavelength-routed optical networks depends on the number of wavelengths required to satisfy a given traffic demand. In this paper, we proposed two symmetrical routing and wavelength-assignment methods for optical networks with a Grid or ShuffleNet physical topology. Here, we consider the case of non-adaptive wavelength routing systems, where the operations performed in nodes are independent of the network traffic load. In this case, the routing differs somewhat from that in adaptive routing networks where the routing function may produce different results at different times. The path followed by a wavelength never changes in non-adaptive wavelength-routing networks. When all N(N-1) node-pairs are to be connected, our methods lower the wavelength requirement to (or close to) its calculated minimum. Symmetry is a basic feature of both these regular topologies, but there are differences in the features within the topologies. Our goal has been to try to make use of the symmetry, and the differences in the native symmetry features, of these regular topologies to yield a lower wavelength requirement.

This paper proposes a new access control scheme called multiple round-robin matching protocol (MRM) for high-speed packet-switched WDM LAN. The architecture is based on a broadcast-and-select star network, where each node has an arbitrary number of fast tunable transceivers. Our scheduling algorithm is simple to implement and can overcome data channel and receiver collision by using a round-robin priority. Simulations demonstrate improved mean delay characteristics with a small number of transceivers at each node.

In this paper, we describe design considerations for inverse dispersion fiber (IDF) whose chromatic dispersion is designed to compensate for that of conventional 1.3 µm zero-dispersion single-mode fiber (SMF). We clarify the appropriate structural parameters for W-type, triple-clad-type and ring-type refractive index profiles to realize a hybrid transmission line composed of SMF and IDF taking into consideration the bending sensitivity and the available wavelength bandwidth that achieves an average chromatic dispersion of below 1 ps/nm/km in the 1.55 µm region. We also show that, when the launched power is less than 0 dBm/ch, a hybrid transmission line composed of SMF and IDF provides better 40 Gbps 8 ch dense wavelength division multiplexing (DWDM) transmission performance than a conventional dispersion compensation scheme with a dispersion compensating fiber (DCF) module.

For the purpose of applying to 50 GHz channel spacing 10 Gb/s DWDM systems, the dispersion reduced fiber Bragg gratings (FBG) is demonstrated. This new FBG is designed by applying in optimized cosine expansion series to the refractive index profile. The 10 π-phase shifts in the refractive index profile realize both square filtering characteristics and linear phase responses resulting in reducing group delay variation in the reflective bandwidth. The FBG, fabricated according to the new design, is tested and shows more than 30 dB isolation for the adjacent channel and less than 10 psec group delay variation in the reflective bandwidth. This small dispersion leads to vast improvement of 10 Gb/s transmission performance. The power penalty of the new FBG is suppressed to 1/6 of that of conventional FBG. Furthermore, the symmetrical refractive index profile, realized by applying a cosine expansion series, shows that these optical characteristics have no dependence of the light launching direction. From these results, this new design offers an FBG suitable for the ADM used in 10 Gb/s DWDM systems.

In modern high-capacity wavelength division multiplexing (WDM) transmission systems, there is increasing demand for large transmission capacity. To achieve this purpose, an L-band (1565-1625 nm) erbium-doped fiber amplifier (EDFA) is very effective method because the conventional silica-based EDF can be used. In EDFAs that used in WDM transmission systems, the gain flatness of EDFA is very important. A passive gain equalizer flattens the gain profile of EDFA. But the gain flatness in L-band deteriorates due to dynamic gain-tilt (DGT) and temperature gain-tilt (TGT) when the operating condition of the EDFA changes, while the EDFAs should maintain the gain flatness even if the operating condition has changed. To solve this problem, we propose an active gain-slope compensation technique for the L-band EDFA using a thulium-doped fiber (TDF). The EDFA actively gain-slope compensated by the TDF compensator keeps the gain profile constant for the wide input power range of more than 8 dB, a wide temperature range of 65 without gain-tilt in a wavelength band between 1575 nm and 1610 nm. Furthermore, the EDFA keeps a low noise figure of less than 7.5 dB.

This paper presents a historical review of fiber technologies from the 1970s till now, focused on design, transmission characteristics, and reliability assurance of silica optical fibers. Discussion is made by dividing the period into two phases; the first phase closing nearly at the end of the 1980s and the second one starting at the same time. As for the first phase, we present designs of graded-index multimode fiber and single-mode fiber, and development of dispersion shifted fiber. Mechanical reliability assurance and loss increase phenomena due to hydrogen are also described. Development of an optical fiber amplifier triggered the start of the second phase. Due to the introduction of WDM transmission systems as well as demand on high bit-rate transmission, fiber dispersion and nonlinearity have become indispensable factors to be taken into consideration for system design and performance evaluation. We discuss novel non-zero dispersion shifted fibers and dispersion compensating fibers, developed to meet the requirements for long distance and high bit-rate WDM transmission systems. Finally, discussions are made on the future research and development items, which are necessary to realize anticipating photonic networks.

In this paper, we propose a synchronous reservation protocol that is efficient for supporting variable-sized messages in a wavelength division multiplexing (WDM)-based local network using a passive star topology. A control channel is used to coordinate message transmission on data channels. Time is slotted with fixed-sized slots. The network can accommodate a variable number of nodes and operate independently of the change in the number of nodes. Therefore, any "new" node can join the network anytime without network re-initialization. Moreover, with the protocol, we can avoid data channel and destination conflicts. We analyze the performance according to the variation of the end-to-end propagation delay with respect to one slot time, and validate the results by simulation.

With the emerging technology of photonic networks, careful design becomes necessary to make most of the already installed fibre capacity. Appropriate numerical tools are readily available. Usually, these are based on the split-step Fourier method (SSFM), employing the fast Fourier transform (FFT). With N discretization points, the complexity of the SSFM is O(N log2N). For real-world wavelength division multiplexing (WDM) systems, the simulation time can be of the order of days, so any speed improvement would be most welcome. We show that the SSFM is a special case of the so-called collocation method with harmonic basis functions. However, for modelling nonlinear optical waveguides, various other basis function systems offer significant advantages. For calculating the propagation of single soliton-like impulses, a problem-adapted Gauss-Hermite basis leads to a strongly reduced computation time compared to the SSFM . Further, using a basis function system constructed from a scaling function, which generates a compactly supported wavelet, we developed a new and flexible split-step wavelet collocation method (SSWCM). This technique is independent of the propagating impulse shapes, and provides a complexity of the order O(N) for a fixed accuracy. For a typical modelling situation with up to 64 WDM channels, the SSWCM leads to significantly shorter computation times than the standard SSFM.

The initial phase alternation of RZ pulses having duty cycle beyond 50% in dispersion-managed-link is found to help stabilize DM solitons transmissions. The stable soliton propagation of such wide RZ pulses should ease the difficulties designing soliton-based DWDM systems due to less spectral occupancy/channel. For the proof of concept, 40 Gbit/s WDM transmissions are numerically investigated and the initial phase alternation improved the transmission distance by the factor of 2 in the soliton-soliton interaction limited regime. The advantage of this concept has also been verified by conducting 40 Gbit/s single and 8 channels WDM transmission experiments using OTDM techniques with initial phase alternation.

Channel bit rates of 40 Gbit/s are the next step after 2.5 and 10 Gbit/s in the SONET/SDH hierarchy. They enable multi Tbit/s transmission of live traffic over a single fiber. All recent optical transmission records concerning aggregate capacitiy per fiber were achieved using this technology. Comparing the limiting effects of 2.5, 10 and 40 Gbit/s system configurations reveals that 40 Gbit/s allows for the longest regenerator free distance on NZDSF. In this paper we describe transmitter and receiver designs as well as results from field trials. The first trial demonstrated a transmission of live traffic with a record aggregate capacity of 3.2 Tbit/s, whereas the second successfully demonstrated a doubling of the channel capacity to 80 Gbit/s using polarization multiplexing with automated polarization control.

Methodologies for more efficient Raman amplification and a more suitable modulation format for 40 Gbit/s WDM unrepeatered transmission are investigated. Management of the fiber effective area is proposed to realize low noise distributed Raman amplification. An Aeff management technique in which low-Aeff fiber is located in a median section instead of the last section, was confirmed numerically and experimentally to improve the OSNR and Q-factor. Carrier-suppressed-return-to-zero (CS-RZ) modulation has the advantage of reducing fiber-nonlinearity effects and permitting denser multiplexing of the wavelengths. 40 Gbit/s 32-channel unrepeatered WDM transmission over 202 km was demonstrated employing the proposed methodologies.

A 1.6-Tb/s dense WDM signal was successfully transmitted over 480 km using the carrier-suppressed return-to-zero (CS-RZ) modulation format. The CS-RZ format was chosen because it exhibited better transmission performance over a wide fiber-input power window than the NRZ and RZ formats in a 40-Gb/s-based WDM transmission experiment with 100-GHz channel spacing, confirming its nonlinearity-insensitive nature in dense WDM systems. With the wide power window of CS-RZ, we achieved stable transmission of 4040-Gb/s WDM signals over a 480-km (680 km) standard SMF line with only the C-band, in which a spectral ripple remained during transmission. Distributed Raman amplification and forward error correction were not used, providing a margin for already installed transmission lines.