Fiber Bragg grating (FBG) optical sensors are state-of-the-art technology that can be integrated into the road structure, providing real-time traffic-induced strain readings and ensuring the monitoring of the road’s structural health. By implementing specific FBG sensors, it is possible to detect each vehicle’s axle count and the induced strain changes in the road structure. In this study, FBG sensors are embedded at the top of the 240-mm-thick cement-treated reclaimed asphalt pavement mixture layer of the road (specifically, 25 mm deep within the road). Optical sensors’ signal interrogation units are used to measure the strain and temperature and collect data of the road’s passing vehicles, starting from passenger cars that have two axles and up to heavy trucks that have six axles. Passenger cars with 2 axles generate a typical (90% events) strain of 0.8–4.1 μm/m, the 2-axle minibus 5.5–8.5 μm/m, 2–3-axle trucks 11–26 μm/m, but 4–6-axle trucks 14–36 μm/m per each axle. A large number of influencing parameters determine the pavement design leading to the great uncertainty in the prediction of the strain at the boundary between the asphalt surface and cement-treated base layers. Real-time strain and temperature measurements help to understand the actual behavior of the pavement structure under an applied load, thus assisting in validating the proposed pavement design.

In this paper we present results from the study of optical signal amplification using Raman assisted fiber optical parametric amplifier with considerable benefits for S-band telecommunication systems where the use of widely used erbium-doped fiber amplifier is limited. We have created detailed models and performed computer simulations of combined Raman and fiber optical parametric amplification in a 16-channel 40 Gbps/channel wavelength division multiplexed transmission system. Achieved gain bandwidth, as well as transmission system parameters—signal-to-noise ratio and bit-error-ratio—were analyzed by comparing the Raman assisted fiber optical parametric amplifier to the single pump fiber optical parametric amplifier. Results show that the 3 dB gain bandwidth in the case of combined amplification is up to 0.2 THz wider with 1.9 dB difference between the lowest and highest gain.

Most optical sensors on the market are optical fiber Bragg grating (FBG) sensors with low reflectivity (typically 7-40%) and low side-lobe suppression (SLS) ratio (typically SLS <15 dB), which prevents these sensors from being effectively used for long-distance remote monitoring and sensor network solutions. This research is based on designing the optimal grating structure of FBG sensors and estimating their optimal apodization parameters necessary for sensor networks and long-distance monitoring solutions. Gaussian, sine, and raised sine apodizations are studied to achieve the main requirements, which are maximally high reflectivity (at least 90%) and side-lobe suppression (at least 20 dB), as well as maximally narrow bandwidth (FWHM<0.2 nm) and FBGs with uniform (without apodization). Results gathered in this research propose high-efficiency FBG grating apodizations, which can be further physically realized for optical sensor networks and long-distance (at least 40 km) monitoring solutions.

In this paper the authors have investigated the performance improvement in long reach optical access system with hybrid optical amplifiers. The apparent options of optical amplification in wavelength division multiplexing systems include the distributed Raman amplifiers, erbium doped fiber amplifiers, and semiconductor optical amplifiers. In our case distributed Raman amplifier is located at the mid-span reach extender which allows for remote amplification in passive network nodes by distributing a Raman pump together with the data signals. In the case of only distributed Raman amplifier in long reach optical access system wavelength division multiplexing exploitation is inefficient. Combining the advantages of different amplifiers allows fast gain dynamics, simultaneous large bandwidth amplification, and the ability to provide gain at any wavelength. Degradation of optical signal quality is evaluated in 10 Gbit/s long reach wavelength division multiplexing optical access system with hybrid distributed Raman-erbium doped fiber amplifier and distributed Raman-semiconductor optical amplifier.

Optical Fiber Communication widely implements Dense Wave Division Multiplexing (DWDM) technique in order to accommodate large number of channels within a limited bandwidth. But, this technology suffers a serious degradation in signal quality due to inter-channel interference. Optical Kerr Effect, in addition to this, worsens the situation. This paper deals with minimization of Four Wave Mixing (FWM) impact, one of the Optical Kerr effects, by using variable channel spacing instead of conventional fixed channel spacing technique. FWM effect generates spurious components at multiple frequencies, whose effective amplitude can be reduced using different channel spacing. Bit Error Rate (BER) observed for different length of fiber has been analyzed with an aim to estimate the difference between variable channel spacing algorithms. Obtained results have shown that BER of 10-11 can be reached with 153.7 km long fiber for fixed channel spacing while the usage of variable channel spacing method keeps the same BER level with 160.5 km long fiber.

The present paper proposes high speed dense 8-channel bidirectional WDM-PON access system where spectrally-uniform ASE source is shared among multiple users for realization of downstream transmission. Upstream transmission is realized by using conventional laser based solution. Proposed system is based on ITU-T DWDM grid and operating at 10 Gbit/s per channel symmetrically on both directions. It is demonstrated that implemented spectrum slicing technology is capable to provide downstream data transmission over 20 km SMF fiber span with BER<;10^-12 by using additional fiber Bragg grating chromatic dispersion compensation module and excess intensity noise reduction by additional semiconductor optical amplifier.