1,721,197 research outputs found
Data regeneration
No full textA regenerator capable of imultaneously removing both phase and amplitude noise from an optical data stream may be a critical component of future optical networks. Radan Slavík explained to Nature Photonics how he and his co-workers realized such a device
Extremely deep long-period fiber grating made with CO<sub>2</sub> laser
No full textWe report on the realization and tuning of a long-period fiber grating-based filter, which is made in a standard telecom optical fiber, with a resonant attenuation of more than 60 dB. This is, to our knowledge, by far the highest published value. The realized filters satisfy requirements of applications which are extremely demanding in terms of the resonant depth or require an exact π-phase shift at the resonance.</p
Coupling to circularly asymmetric modes via long-period gratings made in a standard straight fiber
No full textWe demonstrate long-period fiber gratings made in a straight standard optical fiber via a CO2 laser side irradiation that couples light between modes of different azimuthal symmetry. We show that such coupling can be even stronger than that to the azimuthally symmetric modes, provided the photoinduced asymmetry in the refractive index change across the fiber cross-section is high enough. This suggests that some previously-observed phenomena with CO2-written LPGs not observed with other types of LPGs may be attributed to LPG resonances that couple light into the cladding modes with higher azimuthal symmetry. We show it on an example of bend-induced LPG resonance position tuning with the resonance depth maintained constant.</p
Optical multilayers for LED-based surface plasmon resonance sensors
No full textWe address a structure for surface plasmon resonance (SPR) sensing supporting a symmetric bound surface plasmon, which results in a SPR feature narrower by a factor of 2 compared with that for the conventional configuration. We demonstrate that it enables a low-cost and low-power-consumption LED to be used as a polychromatic light source, which leads to a decrease in the sensor cost and an increase in the sensor miniaturization potential. Further, we show that these advancements are not at the expense of sensor performance in terms of its sensitivity and resolution. We show that the sensor can be designed to have similar sensitivity and even better resolution compared with those for a conventional configuration.</p
Large-band periodic filters for DWDM using multiple-superimposed fiber bragg gratings
No full textThe fight specifications of dense wavelength division multiplexing (DWDM) filters are challenging for any available technologies. In this letter, periodic transmission filters based on superimposed chirped fiber Bragg gratings are designed to have flat amplitude response and nearly constant in-band group delay. These filters should prove to be useful as interleavers and mux/demux filters in DWDM systems
Frequency shift in a fiber laser resonator
No full textA new model that describes the influence of a laser intracavity frequency shifter is proposed. Laser line broadening that is due to the presence of the frequency shift is derived. The theoretical model is validated by experimental results. Multiwavelength operation of this laser is explained.</p
Simultaneous excitation of long and short range surface plasmons in an asymmetric structure
No full textAn asymmetric multilayer structure allowing nearly 100% simultaneous excitation of both symmetric and antisymmetric surface plasmons is proposed. It is shown that the two surface plasmons can be excited at a fixed angle of incidence with polychromatic light or with monochromatic light at different angles of incidence, depending on the design. The structure can be of interest in high-performance surface plasmon resonance sensing and in all-optical signal processing.</p
Ultrahigh resolution long range surface plasmon-based sensor
No full textAn ultra-high sensitive surface plasmon resonance (SPR) sensor based on excitation of a long range surface plasmon was developed. Compared to previous reports, the sensor employs more advanced photonic components like superluminescent diode source and polarization-maintaining fibers, which allowed for dramatic decrease of the sensor detection limit. The attained refractive index detection limit of 2.5 × 10-8 is so far the highest value reported for any SPR-based sensor.</p
Light advancement and delay by linear filters with close to zero resonant transmittance
No full textFilters operated close to the critical coupling were reported to be capable of an increase and decrease of the group velocity. The published examples are ring resonators (feedback-based filter) and Mach-Zehnder filters (no feedback filters). Here we show that these linear filters have, within certain bandwidth, identical filtering characteristics, although they are based on completely different filtering principles. Further, we demonstrate experimentally a long period fiber grating as another no-feedback filter that is capable to perform similar filtering characteristics when operated close to the critical coupling condition. This scheme may be of interest due to inherently large bandwidth provided by long-period fiber grating based filters. In the example given here, filters compatible with systems operating at repetition rates up to 40 GHz are demonstrated.</p
Opticke komunikacni prostredky
No full textReview of optical communications published in the special issue dedicated to the UNESCO Year of Ligh
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