Starting with descriptions of rotational seismology, areas of interest and historical field measurements, the fundamental requirements for rotational seismometers for seismological and engineering application are formulated. On the above basis, a review of all existing rotational seismometers is presented with a description of the principles of their operation as well as possibilities to fulfill formulated requirements. This review includes mechanical, acoustical, electrochemical and optical devices and shows that the last of these types are the most promising. It is shown that optical rotational seismometer based on the ring-laser gyroscope concept is the best for seismological applications, whereas systems based on fiber-optic gyroscopes demonstrate parameters which are also required for engineering applications. Laboratory results of the Fibre-Optic System for Rotational Events & Phenomena Monitoring using a small 1-D shaking table modified to generate rotational excitations are presented. The harmonic and time-history tests demonstrate its usefulness for recording rotational motions with rates up to 0.25 rad/s.

Rotational seismology caused high interest in the investigation on rotational movements generated by earthquakes, mines and existing in engineering structures. The most oppressive aspect of the research in this field are technical requirements for sensors. They have to be extremely sensitive, as well as possess an extremely wide dynamic range of operation from 0.01 Hz to 100 Hz. This paper points out that solutions basing on the optical technology are the most promising devices in comparison to existing mechanical and electromechanical ones. Especially, instruments basing on the von Laue-Sagnac effect seem to be the most appropriate to investigate rotational phenomena due to the fact that they are entirely insensitive to a translational motion, operate without inertia mass and are able to measure rotation rate in wide frequency and amplitude band. The paper presents a new device named FOSREM which, based on the FOG minimum configuration, possesses special solutions that makes it perfect, in author's knowledge, for any rotation sensing. It enables to measure only a rotational component in a wide range of signal amplitude of 2e-8 rad/s - 10 rad/s, as well as in a wide frequency band from DC to 328.12 Hz. The presented performance characteristics, as well as a laboratory investigation confirm FOSREM's opportunity to measure rotation both in seismological observatories and engineering constructions.

In this paper, we report on a simple process of fabrication of micrometer-sized polymer elements (microtips) at the extremities of different type optical fibers, including: standard single mode (SMF-28E+, SM-450), photonic crystal (LMA-10), and polymer (GIPOF-62) ones. The method of microtips manufacturing is based on the phenomenon of photopolymerization which is successfully used for the first time, to the best of our knowledge, to manufacture microtips at photonic crystal and polymer fibers. We discuss the influence of the initial process parameters on the final microtip characteristics (i.e., length, diameter, and profile). The potential applications of such polymer microtips are near-field scanning optical microscopy, coupling light sources with fibers, and sensing.

We demonstrate an experimental study of the chromatic dispersion properties for a series of microstructured fibers (MSFs) dedicated for a supercontinuum generation. With white-light interferometry application we analyze experimentally how the small variations of structural parameters, i.e. an air-hole diameter and a lattice constant, influence dispersion characteristics in different groups of MSFs. Our study provides useful information on how to design the fiber which is less sensitive to the fabrication imperfections. Moreover those investigations are the initial step to the development of the customized or tunable supercontinuum light sources based on MSFs with slightly changed structural parameters which can generate light with a different spectrum range, adapted to a proper application.

We report on low-loss patch cords composed of a highly reproducible low-loss fusion splicing of photonic crystal fibers (PCFs) with a standard single mode fiber (SMF). Distinct from other papers in this area we report on the results for different types of PCFs, including LMA fibers with similar to a SMF core size and a mode field diameter (MFD), as well as polarization maintaining (PM) Bow-Tie PCF with an elliptical GeO ₂ doped core and also a suspended-core (SC) PCF with a tiny core. We show that all studied splices between SMF and PCFs exhibit dispersive and non-reciprocal, in view of a light propagation direction, transmission losses. Defined as a larger decrease of a transmitted optical power comparing both propagation directions, achieved splicing losses, are equal to 0.46 ±0.03 dB, 0.34±0.01 dB, 0.67 ±0.17 dB and 3.09 ±0.36 dB at 1550 nm for LMA8, LMA10, Bow-Tie PCF and SC PCFs, respectively. Moreover, additionally to developed low-loss splicing, we report on low-loss patch cords for all mentioned above PCFs spliced on both ends with SMF pigtails ended with FC/APC connectors achieving the total losses at 1550 nm equal to 1.07 ±0.07 dB for LMA8, 0.72 ±0.20 dB for LMA10, 1.30 ±0.06 dB for Bow-Tie PCF, and 9.36 ±0.20 dB for SC PCF.