A closed-form capacity expression for polarization-multiplexed coherent MIMO radio-over-fiber (RoF) links at millimeter-wave bands is derived and the impact of the fiber's polarization rotation and the wireless antenna misalignment on the MIMO channel capacity is revealed. The analytical results are validated via an indoor W-band (75-110 GHz) 10-Gbaud MIMO-RoF transmission experiment.

We analyze the throughput of fixed-length, variable-capacity (FL-VC) packet technology in OPS MANs with lengths up to several tens of kilometers. Compared to conventional OPS networks using fixed-bit-rate packets, FL-VC often offers throughput increases of ≃50% to TCP flows, and of ≃100% to UDP flows, under realistic traffic patterns. Throughput also increases with respect to equivalent topologies where switches have random-access buffers.

Mode division multiplexing (MDM) over wavelength division multiplexing (WDM) network is studied, particularly focusing on low differential mode group delay (DMGD) two-mode fiber (TMF) link in a wide spectral range. Here, the DMGD is defined as the group delay between the two guided modes, LP01and LP11modes. For the starter, We will revisit an invention of the original TMF in late 70's, followed by the DMGD-compensated TMF link and crosstalk between two mode channels due to the mode coupling effect. Next, in order to explore the feasibility of "real-time" digital signal processing (DSP) for multiple-input multiple-output (MIMO) transmission system for equalizing the mode channel crosstalk, the computational complexity of MIMO DSP will be evaluated. As a consequence, a criterion of the DMGD value to enable the realtime MIMO DSP is derived. Finally, against a backdrop of 560% predicted traffic surge of metro area network (MAN) by 2017, a deployment scenario of MDM over WDM MAN is presented as the solution, and the MDM node architecture will be discussed.

A frequency-reconfigurable radio-over-fiber transmitter is designed and demonstrated with an optical frequency comb source for millimeter-wave and terahertz signal transmission over a fiber-wireless hybrid link. Optical-to-radio and radio-to-optical converters with a high-speed photomixer and frequency-heterodyne technique successfully perform coherent quadrature-phase-shift-keying signal generation and reception in the optical domain at 90 GHz and 300 GHz. A digital radio receiver also receives and demodulates the transmitted QPSK signal at 300 GHz with the same bit error rate behavior as in an optical link.

A dynamic routing and wavelength allocation technique with interplay between physical and network layer parameters encompassing four-wave mixing (FWM) awareness and the teletraffic performance of wavelength-routed optical networks has been proposed under a distributed approach. In this paper we present an online RWA encompassing FWM-induced crosstalk based upon an impairment-constraint-based routing (ICBR) called FWM-aware dynamic RWA. Our model design assumes a realistic scenario and leads to better network performance comparing to previous work approaches. A fast computational scheme in order to minimize the time of establishing a lightpath dynamically, is also evaluated, for this purpose a precomputed matrix of FWM crosstalk products is proposed and introduced into the mxFWM-aware RWA. The approach is validated through simulations showing improvement up to 30-50 percent on the provisioning time of lightpaths for different network topologies compared to a full on-line computational scheme or FWM-aware RWA.

In our previous studies, an optical-code-division multiplexing (OCDM)-based network architecture has been proposed to improve the wavelength utilization and to provide finer bandwidth granularities to users. However, since up-to-date all-optical regeneration technologies are still immature, signal quality degradation at intermediate nodes is considered as a crucial problem in transparent optical networks. Because the remaining noises may propagate, and be accumulated along the light-path, which eventually result in unacceptable signal quality. In this paper, we first define a cycle attack problem due to multi-access interference (MAI) propagation in transparent OCDM-based networks, which may cause severe service disruption. A depth-first-search (DFS)-based algorithm is proposed to diagnose such cycle attacks and a heuristic wavelength assignment called advanced first-fit (AFF) scheme taking cycle attacks into account is found to be a simple but effective approach mitigating the cycle attack impacts by computer simulations.

Many target localization techniques based on received signal strength indicator (RSSI) assume a prior knowledge of a channel model and its parameters for an area where a target node is localized. This is a limiting factor since an intensive pre- measurement campaign is required to determine the model and its parameters. Basing on channel measurement campaigns in different areas we confirmed that the variation in the RSSIs of the IEEE 802.15.4 signal can be described by a two-layer model. We therefore propose a novel target localization method with no prior knowledge of model parameter values. The method is based on a joint maximum likelihood target localization and channel model parameters estimation. The proposed method was experimentally verified in real environments and the results show that the location estimation accuracy outperforms the accuracy of the conventional method where the values of the channel model parameters are known in advance.

In this paper, an OCDM-based multi- granularity optical cross-connect (MG-OXC) is proposed to enable the optical path switching in bandwidth granularity finer than the wavelength-based path. Such an optical path switched by OCDM-based MG-OXC is called OCDM label-switched path (OCDM-LSP), which is capable of hybrid optical code (OC)/wavelength conversion along the path from a source to destination. With distinct OCs, OCDM-LSPs can share a single wavelength without any synchronization mechanism and be discriminated by ultra- fast optical correlation. The asynchronous ability and OC conversion distinguish the OCDM-LSP from Packet-LSP or TDM-LSP in resolving granularity problem in wavelength- based path. Based upon our proposal, all-optical optical path provisioning including F-LSP, WB-LSP, L-LSP and OCDM- LSP can be realized in the transport layer. Simulation is conducted and the results show the proposed OCDM-switching has gained a 2 order of blocking probability reduction even though only 5 OCs are employed. Furthermore, OC conversion in OCDM-LSP is proved to be another benefit for high flexibility in optical path provisioning and blocking performance improvement comparing to TDM-LSP.

Location estimation is one of the most attractive applications in wireless sensor networks. In this paper, we propose a new iterative location estimation method using radio signal strength indicators (RSSIs) not only among target and fixed nodes but also among target nodes. Our computer simulation shows that, if the RSSIs among target nodes are available whose locations are unknown so should be estimated, we can improve the location estimation performance by means of the proposed iterative method

Many applications of wireless sensor networks require to process data cooperatively and to combine information from multiple nodes simultaneously. One of such applications is localisation and tracking where information from many nodes is processed at the same time to accurately estimate targets' positions. However, in case of centralised localisation and tracking applications based on received signal strength indicator (RSSI), where the anchor nodes forward their measured RSSI information to a control centre, the narrow bandwidth of wireless communication link limits the amount of data being forwarded to the control centre. As a result, it cannot receive all the data from the anchor nodes as the number of target nodes increases, and therefore cannot estimate all targets' positions. Thus, we propose a traffic reducing method based on limiting the RSSI information being forwarded and evaluate the proposed method by localising target positions in real environments using maximum likelihood estimation. The results show between 50% and 80% traffic load reduction without severely affecting the estimation accuracy. In addition, the location estimation accuracy is improved at some cases.

In a distributed wavelength-routed network, a lightpath request is blocked when its assigned wavelength is already occupied by another lightpath request. Conventional studies assume that a wavelength for the lightpath is selected randomly in the distributed lightpath setup method. However, this random selection method causes unnecessary blocks of lightpath requests, even when the arrival rate of requests is low. In this paper, we develop a novel method for assigning wavelengths, based on the first-fit algorithm. In our proposed method, the intermediate nodes forecast the wavelength that will be selected at the destination node, so that the subsequent lightpath requests avoid the forecasted wavelengths. The forecasted wavelength is thus kept available until the corresponding request reserves it, which prevents wavelength conflicts with other lightpath requests. Computer-simulated performance comparison showed that our method reduces the blocking probability by more than one order of magnitude compared to random selection.

This paper describes new optical switching architectures supporting asynchronous variable-length packets. Output line contention is resolved by optical delay line buffers. By introducing a WDM technology, a parallel buffer can be equipped with multiple wavelengths on the optical delay line buffer. Using an ultrafast photonic label processing technique, an implementation of our architecture would be fast enough for packet scheduling that selects the appropriate output port, wavelength, and delay line buffer. To evaluate the switch performance, we model an output port of our switch as a multi-server and multi-queue system where each server corresponds to a wavelength and where each arriving packet joins the shortest queue. We use an approximate analytic approach to evaluate the switch performance. The results of the analysis and of simulation experiments show that the use of the WDM technique can greatly improve the switch performance in terms of packet loss probabilities.

Lightwave networks realized through code division multiple access techniques are extensively studied to determine their ultimate capabilities. Here, these concepts are extended to network implementation by introducing an optical code division multiplexing (OCDM) multihop strategy using optical coding. It is shown that this approach is effective in scaling up existing wavelength division multiplexing (WDM) networks without a significant drain of the wavelength resources. The concept of a virtual optical code path (VOCP) is introduced within the transport layer of the network. It is demonstrated that this is a potential solution to wavelength path (WP) allocation problems which may plague WDM based transport networks of the future. Crucial to the VOCP concept is optical code conversion. The interplay between this added functionality and the optical cross-connect is highlighted; the optical cross-connect serves to establish VOCP/VWP (virtual wavelength path) in the hybrid transport layer. An example of optical code conversion is introduced. It is based on coherent OCDM principles in which bipolar phase-shift keyed (PSK) optical pulse sequences are used as the signature codes. Error-free code conversion using a four-chip optical encoder/decoder is successfully performed at 1.24 Gbit/s. The results show the feasibility of high bit rate OCDM transmission with optical code conversion.

A novel generation and delivery of many millimeter (mm)-wave signals over optical frequency division multiplexing (OFDM) networks is experimentally demonstrated. A number of lightwaves are selected from a special class of coherent multifrequency light source and multiplexed. The OFDM signals are transmitted over an optical fiber network. After being demultiplexed, each pair of the lightwaves is delivered to the base station (BS) and converted into a mm-wave signal by optical self-heterodyning. In the experiment, two 60 GHz mm-wave signals having the 3dB linewidths of less than 0.3 kHz are successfully generated with a good carrier-to-noise power ratio (CNR) of 21 dB.

Novel code division multiple access (CDMA) fiber optic networks based on spatial frequency spread spectrum for image transmissions are proposed. Two key technologies are the parallel fiber optic transmission of spatially encoded images and parallel access to image data through optical spatial encoding and decoding. The temporal signature sequences used in conventional time-domain CDMA are replaced by two-dimensional (2-D) signature patterns to encode and decode binary image pixels. This enables the fully parallel access and transmission of images. The fundamental rules and methodology to construct optical orthogonal signature patterns (OOSP) are presented. Furthermore, it is shown that the all-optical implementation of the proposed system is feasible by utilizing optically addressable spatial light modulators in both the spatial encoder and the decoder along with multicore fibers as the parallel image transmission medium. The predicted overall throughput can reach 10 Tb/s.>