All-optical Paths Research Articles

Estimation of Infrared Stellar Flux Based on Star Catalogs with I-GWO for Stellar Calibration

As on-orbit space cameras evolve toward larger apertures, wider fields of view, and deeper cryogenic environments, achieving absolute radiometric calibration using an all-optical path blackbody reference source in orbit becomes increasingly challenging. Consequently, stars have emerged as a novel in-orbit standard source. However, due to differences in camera bands, directly obtaining the stellar radiance flux corresponding to specific camera bands is not feasible. In order to address this challenge, we propose a method for estimating radiance flux based on the MSX star catalog, which integrates a dual-band thermometry method with an improved grey wolf optimization (I-GWO) algorithm. In an experiment, we analyzed 351 stars with temperatures ranging from 4000 to 7000 K. The results indicate that our method achieved a temperature estimation accuracy of less than 10% for 83.5% of the stars, with an average estimation error of 5.82%. Compared with previous methods based on star catalogs, our approach significantly enhanced the estimation accuracy by 75.4%, improved algorithm stability by 91.3%, and reduced the computation time to only 3% of that required by other methods. Moreover, the on-orbit star calibration error using our stellar radiance flux estimation method remained within 5%. This study effectively leveraged the extensive data available in star catalogs, providing substantial support for the development of an infrared star calibration network, which holds significant value for the in-orbit calibration of large-aperture cameras. Future research will explore the potential applicability of this method across different spectral bands.

Thermal design of all-optical path cold chain based on transmission-type cryogenic optical infrared camera

Thermal design of all-optical path cold chain based on transmission-type cryogenic optical infrared camera

All-Optical Monitoring Path Computation Using Lower Bounds of Required Number of Paths

All-Optical Monitoring Path Computation Using Lower Bounds of Required Number of Paths

Towards the realistic planning of GMPLS-based optical transport networks

The multi-granular switching concept defined in Generalized Multiprotocol Label Switching (GMPLS) is expected to be a future-proof solution for mitigating the Optical Crossconnet scalability problems associated with the skyrocketing growth of traffic in optical transport networks. In this paper, we address the problem of planning the GMPLS-based (or multi-granular) transport network with color (or label) conversion and signal regeneration capabilities. The objective of the problem is to minimize the total weighted port count in the transport network. The novelty of this problem lies in the incorporation of the following for the first time: (1) considering all traffic granularities defined in GMPLS; (2) allowing wavelength, waveband, and fiber conversions; (3) considering the optical-reach limitation of optical signals; and (4) customizing the optical reach of all-optical paths. Due to the computational complexity of the problem, we propose various efficient heuristics that are capable of solving large-sized problems in a reasonable amount of time. In order to achieve the best possible solution to the planning problem, a comprehensive evaluation of different heuristic variations through illustrative examples and simulations is conducted. The results also provide valuable insights into many issues that can contribute to further research and development in this area.

Field Trial of All-Optical Networking Controlled by Intelligent Control Plane With Assistance of Optical Performance Monitors

A field trial of all-optical networking by an intelligent control plane based on generalized multiprotocol label switching (GMPLS) technologies was successfully conducted with the assistance of optical performance monitors (OPMs) capable of monitoring the in-band optical signal-to-noise ratio (OSNR). In the field trial, the GMPLS control plane was applied to not only fast provisioning of all-optical paths but also to end-to-end restoration of optical paths triggered by OPMs. Reliable and stable network operation was achieved as a result of applying the GMPLS control plane and OPMs.

Demonstration of a transparent router for wavelength-hopping time-spreading optical CDMA

We propose and demonstrate a two-dimensional wavelength-hopping time-spreading optical code division multiple access (OCDMA) node architecture for all-optical path networks. An OCDMA-based network can provide optically transparent and reconfigurable paths for on-demand high-bandwidth optical connections. The network node consists of parallel code converter routers (PCCRs), which perform routing by passive code conversion, the destination address of the data sent being an OCDMA code. We present an experimental demonstration of this OCDMA node in a 4-station mesh network operating at 253Gchips/s with a single user bit rate of 2.5Gb/s. We show the capability of the node to create reconfigurable code paths (CPs) and virtual code paths (VCPs). Our proposed architecture provides an all-optical method to create reconfigurable paths, while reducing switching delays and node complexity. Due to the inherent flexibility of OCDMA, path networks can rapidly respond to failure or changes in load condition while accommodating a large number of users.

Field test of GMPLS all-optical path rerouting

Router-to-router all-optical wavelength path rerouting using generalized multiprotocol label switching protocol has been successfully carried out including photonic cross-connect and dense wavelength-division-multiplexing equipment. The rerouting time was measured to be shorter than 7 s.

On routing of wavebands for all-to-all communications in all-optical paths and cycles

We discuss a model of the all-optical communication technology and an implementation of a simple task, all-to-all, in simple topologies like paths and cycles. The model assumes a single interval (variant of band-pass) filter extracting signal wavelengths for processing and forwarding in intermediate communication nodes. In an attempt to use a minimum number of wavelengths, we give lower and upper bounds on the cardinality of the spectrum used in four cases arising from different assumptions on the topology and the filters. In particular, we propose efficient schedules of directed paths between all pairs of nodes in graphs of maximum node degree two, under the assumption of either a “linear” or “wrapped-around” wavelength spectrum.

Field trial of automatic chromatic dispersion compensation for 40-Gb/s-based wavelength path protection

We report the results of the field trial of generalized multiprotocol label switching-based 40-Gb/s wavelength path protection by photonic cross-connect. In the trial, an automatic chromatic dispersion (CD) compensator was applied to maintain the quality of a signal after protection operation to compensate for the residual CD along the wavelength path. From the results of the field trial, we have made sure that the automatic CD compensation system is essential for the future all-optical wavelength path network.

Traffic engineering featuring dynamic lightpath provisioning in multilayer GMPLS optical networks

Wavelength-routed networks are viewed as less flexible than IP-routed networks because of the dedicated nature of optical path and incurred optical layer constraints, e.g., wavelength continuity constraints. However, current wavelength-routed networks operating in the WDM environment are empowered with the potential of dynamic and fast provisioning of high-bandwidth optical paths. This potential is currently being addressed by intelligent traffic engineering (TE) on multilayer networks that combine both a broadband optical layer and a grooming-capable electronic layer. We propose a dynamic TE scheme within the framework of multilayer generalized multiprotocol label switching (GMPLS), which takes into consideration the simple nature of an all-optical (OOO) path, the flexibility and grooming efficiency of optical-electrical-optical (OEO) connection, and the support of traffic quality of service (QoS). It optimizes the utilization of OOO and OEO connections in a hybrid fashion through the concept of lightpath tunneling that can adapt to real-time traffic demands. Simulations based on this TE scheme show that the optical transceiver requirement it core nodes can be reduced to only ~20% of that of the IP-routed networks without sacrificing performance. This TE scheme can also be adapted to network scenarios where very limited numbers of transceivers are deployed.

Regular multihop logical topologies for lightwave networks

Several government- and industry-funded prototyping and development activities in WDM optical networks are being conducted at various R&D centers. Optical networks can be deployed on top of an existing physical fiber plant that can provide a transparent all-optical signal path to its upper layer, thereby providing broadband services. For instance, an all-optical layer between the physical and ATM layers in a B-ISDN network will significantly improve both efficiency and flexibility for the provision of broadband services. One attractive feature of optical networks is the ease of its logical reconfigurability, i.e., any desired logical network topology can be embedded on top of any given physical fiber plant, subject to the limitations on the number of available wavelengths and transceivers. The logical topologies can be broadly classified into two categories: arbitrary and regular. Nodal connectivity patterns in regular topologies are very systematic and well defined, which simplifies routing and management operations. However, it is difficult to add an arbitrary number of nodes to a regular topology and still maintain its well-defined structure. Over the past few years, several regular logical topologies have been proposed for optical networks. In this article we provide brief descriptions of these regular logical network topologies and a comparative study of their various performance metrics, e.g., average hop distance (viz. network utilization), routing, fault tolerance, and scalability.

A Symmetric Processor Array with Synchronous Optical Buses and Switches

A modified processor array with synchronous optical buses and switches for time division multiplexed optical communications is proposed. Compared with a previously proposed processor array architecture, our architecture features better flexibility, improved packet slot utilization rate and reduced average packet response time, while preserving all-optical communication paths.

Multiple-star wavelength-router network and its protection strategy

A wavelength division multiplexed (WDM) multiple-star network and its accompanying path and router protection strategies are proposed for interconnecting N major switch nodes in a national-scale telecommunications network. For a single path failure and uniform traffic matrix, fiber requirements are shown to be less than for a WDM ADM ring, while providing greater resilience to multiple path failures. Adding and dropping only whole wavelength channels between node pairs is found to lead to severe design instabilities and overinvestment in fiber, and time-sharing of wavelength channels is recommended to minimize fiber quantities. A star network capable of interconnecting N=22 switch nodes and an all-optical path protection switching method are verified experimentally, using a 16-channel 2,5-Gbit/s WDM system and a 22/spl times/22-port bulk-optics wavelength multiplexer as the hub router. Protection switching speeds within 50 ms are projected for a national-scale network.