Since the introduction of optical fiber technology in the field of sensor based on the technique of surface plasmon resonance (SPR), fiber-optic SPR sensors have witnessed a lot of advancements. This paper reports on the past, present, and future scope of fiber-optic SPR sensors in the field of sensing of different chemical, physical, and biochemical parameters. A detailed mechanism of the SPR technique for sensing purposes has been discussed. Different new techniques and models in this area that have been introduced are discussed in quite a detail. We have tried to put the different advancements in the order of their chronological evolution. The content of the review article may be of great importance for the research community who are to take the field of fiber-optic SPR sensors as its research endeavors.

Fiber-Optic Sensors Based on Surface Plasmon Resonance: A Comprehensive Review

The concept of a Microstructured Optical Fiber-based Surface Plasmon Resonance sensor with optimized microfluidics is proposed. In such a sensor plasmons on the inner surface of large metallized channels containing analyte can be excited by a fundamental mode of a single mode microstructured fiber. Phase matching between plasmon and a core mode can be enforced by introducing air filled microstructure into the fiber core, thus allowing tuning of the modal refractive index and its matching with that of a plasmon. Integration of large size microfluidic channels for efficient analyte flow together with a single mode waveguide of designable effective refractive index is attractive for the development of integrated highly sensitive MOF-SPR sensors operating at any designable wavelength.

Design of the Microstructured Optical Fiber-based Surface Plasmon Resonance sensors with enhanced microfluidics

Optical Surface plasmon resonance (SPR) biosensors represent the most advanced and developed optical label-free biosensor technology. Optical SPR biosensors are a powerful detection and analysis tool that has vast applications in environmental protection, biotechnology, medical diagnostics, drug screening, food safety and security. This article reviews the recent development of SPR biosensor techniques, including bulk SPR and localized SPR (LSPR) biosensors, for detecting interactions between an analyte of interest in solution and a biomolecular recognition. The concepts of bulk and localized SPs and the working principles of both sensing techniques are introduced. Major sensing advances on biorecognition elements, measurement formats, and sensing platforms are presented. Finally, the discussions on both biosensor techniques as well as comparison of both SPR sensing techniques are made.

Surface plasmon resonance based biosensor technique: a review

Publisher Summary Polarization mode dispersion (PMD) is a linear effect that can be compensated in principle. In an ideal circularly symmetric fiber, the two orthogonally polarized modes have the same group delay. However, in reality, fibers exhibit a certain amount of birefringence because of imperfections in the manufacturing process or mechanical stress on the fiber after manufacture. It is noted that fluctuations in the polarization mode and fiber birefringence produced by the environment lead to dispersion that varies statistically with time and frequency. PMD causes different delays for different polarizations and when the difference in the delays approaches a significant fraction of the bit period, it leads to pulse distortion and system penalties. Environmental changes— including temperature and stress—cause the fiber PMD to vary stochastically in time. PMD, illustrating the basic concepts, the measurement techniques, the PMD measurement, the PMD statistics for first- and higher orders, the PMD simulation and emulation, the system impairments, and the mitigation methods has been summarized in the chapter. Both the optical and the electrical PMD compensations are considered.

Polarization-Mode Dispersion

We demonstrate by 3D numerical calculations that the interaction of a single quantum emitter with the electromagnetic field is both enhanced and directed by a nano-optical Yagi-Uda antenna. The single emitter is coupled in the near field to the resonant plasmon mode of the feed element, enhancing both excitation and emission rates. The angular emission of the coupled system is highly directed and determined by the antenna mode. Arbitrary control over the main direction of emission is obtained, regardless of the orientation of the emitter. The directivity is even more increased by the presence of a dielectric substrate, making such antennas a promising candidate for compact easy-to-address planar sensors.

Enhanced directional excitation and emission of single emitters by a nano-optical Yagi-Uda antenna.

In this letter, we demonstrate very high-resolution optical spectrometry based on stimulated Brillouin scattering between a swept-tuned laser and a test optical signal. Measurement principles are presented along with spectral measurements of unmodulated and modulated optical sources showing 0.08-pm resolution and 80-dB dynamic range.

Very high resolution optical spectrometry by stimulated Brillouin scattering

A new ‘in-line’ fibre-optic sensor based on the excitation of surface plasmons in a thin metal film deposited in the polished cladding of the fibre is presented. Optical-power transmission characteristics of the device, for TM-polar- ized light, have been both experimentally and theoretically investigated. The obtained results show the feasibility of practical designs with in-line fibre-optic configuration for a large range of optical sensor applications.

New ‘in-line’ optical-fibre sensor based on surface plasmon excitation

The resonant excitation of metal-clad modes, including fundamental and higher-order modes, in a multilayer structure deposited on the polished cladding of a single-mode optical fiber is theoretically analyzed and experimentally demonstrated. The excitation of metal-clad modes is shown as a resonant power transfer from the fiber to the metal-clad mode that takes place for an external refractive-index value such that the effective index of the metal-clad mode reaches the cladding level. The observed attenuation on the TM polarization provides a suitable transducing mechanism for refractive-index sensor devices as well as the principle for developing tunable wavelength-polarized filters with a wide range of optical performance characteristics.

Single-mode, optical-fiber sensors and tunable wavelength filters based on the resonant excitation of metal-clad modes.

Suitable use of stimulated Brillouin amplification (SBA) effect for selective single peak amplification in an optical frequency comb is demonstrated to provide high accuracy in optical frequency metrology. A pump wave generated by a tunable laser source (TLS) is used to stimulate SBA of such optical comb along an optical fiber and selectively amplify only one single peak of the comb. Nature of SBA preserves both linewidth and absolute wavelength position of the selected comb peak. All of these features result in a simple, robust and compact all in fiber system. Relative optical frequency accuracy in the order of Hz is confirmed.

All in fiber optical frequency metrology by selective Brillouin amplification of single peak in an optical comb

A high-resolution light intensity spectrum analyzer technique to derive the RF modulation spectrum of optical signals is presented and experimentally confirmed. It uses the XPM nonlinear effect in a dispersion shifted fiber to obtain the light intensity spectrum, and a Brillouin optical filtering method to implement the high resolution spectrometric analysis. Measured RF spectra of PRBS modulated optical signals at 2.5 Gb/s and 10 Gb/s are presented and compared with their corresponding ones obtained in the electrical detection domain to confirm the capabilities of the method. Influence of fiber electrostriction effect is measured and analyzed.

J. Pelayo

Papers

Very high resolution optical spectrometry by stimulated Brillouin scattering

New ‘in-line’ optical-fibre sensor based on surface plasmon excitation

Single-mode, optical-fiber sensors and tunable wavelength filters based on the resonant excitation of metal-clad modes.

All in fiber optical frequency metrology by selective Brillouin amplification of single peak in an optical comb

High resolution light intensity spectrum analyzer (LISA) based on Brillouin optical filter.