In-service structural health monitoring (SHM) of engineering structures has assumed a significant role in assessing their safety and integrity. Fibre Bragg grating (FBG) sensors have emerged as a reliable, in situ, non-destructive tool for monitoring, diagnostics and control in civil structures. The versatility of FBG sensors represents a key advantage over other technologies in the structural sensing field. In this article, the recent research and development activities in structural health monitoring using FBG sensors have been critically reviewed, highlighting the areas where further work is needed. A few packaging schemes for FBG strain sensors are also discussed. Finally a few limitations and market barriers associated with the use of these sensors have been addressed.

Fibre Bragg gratings in structural health monitoring—Present status and applications

The growing amount of data that is generated every year creates an urgent need for new and improved data storage methods. Nanomaterials, which have unique mechanical, electronic and optical properties owing to the strong confinement of electrons, photons and phonons at the nanoscale, are enabling the development of disruptive methods for optical data storage with ultra-high capacity, ultra-long lifetime and ultra-low energy consumption. In this Review, we survey recent advancements in nanomaterials technology towards the next generation of optical data storage systems, focusing on metallic nanoparticles, graphene and graphene oxide, semiconductor quantum dots and rare-earth-doped nanocrystals. We conclude by discussing the use of nanomaterials in data storage systems that do not rely on optical mechanisms and by surveying the future prospects for the field. New solutions are needed to meet the growing demand for data storage systems with ultra-high capacity, ultra-long lifetime and ultra-low energy consumption. Nanomaterials, including metal nanoparticles, graphene and graphene oxide, semiconductor quantum dots and rare-earth-doped nanocrystals, hold promise for the next generation of optical data storage methods.

Nanomaterials for optical data storage

This paper reports comprehensive experimental results on a femtosecond code-division multiple-access (CDMA) communication system test bed operating over optical fiber in the 1.5 /spl mu/m communication band. Our test bed integrates together several novel subsystems, including low-loss fiber-pigtailed pulse shapers for encoding-decoding, use of dispersion equalizing fibers in dispersion compensated links for femtosecond pulse transmission and also in femtosecond chirped pulse amplification (CPA) erbium doped fiber amplifiers (EDFAs), and high-contrast nonlinear fiber-optic thresholders. The individual subsystems are described, and single-user system level experimental results demonstrating the ability to transmit spectrally encoded femtosecond pulses over a 2.5-km dispersion compensated fiber link followed by decoding and high contrast nonlinear thresholding are presented.

Femtosecond encoder-decoders and ultrafast nonlinear thresholders and their integration in a femtosecond code division multiple access communication system test-bed

Fiber- or rod-based optical source featuring a large-core, rare-earth-doped photonic-crystal device for generation of high-power pulsed radiation and method

A method and apparatus for drug product tracking (or other pharmaceutical, health care or cosmetics products, and/or the packages or containers they are supplied with) using diffraction grating-based encoded optical identification elements (8) includes an optical substrate (10) having at least one diffraction grating (12) disposed therein. The grating (12) has one or more colocated pitches A which represent a unique identification digital code that is detected when illuminated by incident light (24). The incident light (24) may be directed transversely from the side of the substrate (10) (or from an end) with a narrow band (single wavelength) or multiple wavelength source, and the code is represented by a spatial distribution of light or a wavelength spectrum, respectively, or a combination thereof. The encoded element (8) may be used to label any desired item, such as drugs or medicines, or other pharmaceutical or health care products or cosmetics. The label may be used for many different purposes, such as for sorting, tracking, identification, verification, authentication, anti-theft/anti-counterfeit, security/anti-terrorism, or for other purposes. In a manufacturing environment, the elements (8) may be used to track inventory for production information or sales of goods/products. Such labeling provides product identification at the pill or liquid medicine level, which provides traceability of these products to their manufacturer, thereby reducing counterfeit products in the marketplace. Also, the elements (8 )may be incorporated into a film, liquid, coating or adhesive tape at attached to the product package.

Method and apparatus for drug product tracking using encoded optical identification elements

Programmable waveguide coders (601) are disclosed that include one or more corrugation segments (609) and one or more spacer segments (613) formed on or in a waveguide defined by a core (605) and the spacer segments (613) are independently controllable with voltages applied to each segment's electrodes (617, 618). The spacer segments (613) permit application of a phase modulation to an input while the corrugation segments act as tunable gratings, wherein a center grating wavelength is tunable by applying a voltage to an electrode associated with the corrugation segment (609). In some embodiments, coders include only corrugation segments (609) or only spacer segments (613). Such coders can be strain tuned or thermally tuned. The coders can be programmatically tuned to code or decode a time-wavelength code or other code.

Dynamically reconfigurable composite grating filters for temporal waveform processing

Encoders and decoders for applying composite codes to optical data signals include encoders (211, 231) and decoders (243, 261) for applying both subcodes and supercodes. The subcodes have a duration selected as less than or equal to an interchip duration or a chip duration of the supercodes. The encoders (211, 231) and decoders (243, 261) ('coders') include fiber Bragg gratings configured to encode or decode a subcode, a supercode, or a composite code. By coding with a subcode coder, a coder is reconfigurable by selecting different subcodes or supercodes. Communication systems and methods using composite codes are also described.

Codes, methods, and apparatus for optical encoding and decoding

Communication systems and methods are disclosed that route, detect, and decode encoded optical signals at network nodes based on channel codes assigned to the network nodes. In an example communication system, a network hub includes a channel selector that encodes an optical signal with a channel code assigned to one or more network nodes. The channel selector is configured to encode based on a channel selection signal provided to the channel selector and can include one or more fiber Bragg coders. Code-switched communication systems can include one or more nodes configured in ring, tree, or bus architectures.

Code-switched optical networks

Code-multiplexed communication systems (100), apparatus, and methods include coders (Fig.1) that encode and decode data streams with synchronous, substantially orthogonal codes. Code-multiplexed communications systems (100) encode data signals with such codes to control levels of decoding artifacts such as cross-talk at times or time intervals in which data is recovered. Some systems are based on synchronous, orthogonal codes that are obtained from complex orthogonal vectors. In an example, a three-level temporal-phase code that includes nine code chips is used to encodes and decodes data signals is a seven-channel communication system.

Communication systems and apparatus with synchronous orthogonal coding

An optical phased array transmitter/receiver includes a plurality of waveguides each including an optical fiber and a light source coupled to the fibers in the waveguides. At least one grating is coupled to the fiber of each waveguide and at least one phase shifter coupled to the fiber of at least one waveguide. The phase shifter controls a phase profile of light passing through the fiber to control a profile of a laser beam reflected at the grating. The gratings reflect light passing through the fibers outside of the optical coder to form a laser beam shaped and directed by the grating and phase shifters. Further, a detector is coupled to the waveguides that is enabled to receive light reflected off the gratings. Other embodiments are described and claimed.

Optical phased array transmitter/receiver

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