Springer Science and Business Media LLC

The explosive growth in the need of massive information rates and number of service users has lead to increased attention towards novel point-to-multipoint transmission links capable of meeting the requirements of next generation-passive optical networks (NG-PON). This work proposes an ultra-high information capacity NG-PON downstream transmission architecture incorporating hybrid wavelength-division multiplexed (WDM) and polarization-division multiplexed (PDM) signals. 4-independent WDM channels with 100 GHz spacing, each transmitting 112 Gbps PDM beam using 16-quadrature amplitude modulated (QAM) signals are realized. The analytical investigation of the proposed hybrid W-PDM-based NG-PON scheme is realized for varying number of optical network units (ONUs) i.e. 64, 128 and 256 under the effect of non-linearities, fiber attenuation and dispersion. The performance is evaluated using bit-error rate, error vector magnitude, received optical power, and constellation plots of the signals at the ONUs as the metrics for performance. Results report a reliable transmission of 4 $$\lambda$$ $$\times$$ 112 Gbps information along 90, 75 and 62 km for 64, 128 and 256 ONUs respectively. The proposed work provides an analytical understanding of high-capacity NG-PON system employing hybrid W-PDM techniques for varying number of end users.

Infrared small target detection is a crucial part of infrared search and track system, and it has been a significant research topic in the past decades. Inspired by previous studies showing that phase spectrum of quaternion Fourier transform (PQFT) great superiority in salient region extraction and the desirable characteristics of multi-scale, multi-direction and shift-invariant with non-subsampled shearlet transform (NSST), a new target detection method is proposed based on NSST and PQFT in this paper. The original image is first subjected to NSST decomposition to obtain a low frequency component and four high frequency components by NSP. Next, directional localization is achieved by shearing filters which provides multi-directional decomposition. Then, four direction high frequency sub-images decomposed by NSST are introduced as four data channels of PQFT. The reconstruction map that highlights the salient region in the time domain is computed using the inverse PQFT. Lastly, the real target is directly segmented by an adaptive threshold. The proposed method is validated by five test sequences. The experimental results show that our method is superior to other traditional methods in terms of robustness and effectiveness in complex background.

Over last decades, the free space optics (FSO) emerged as most prominent way of communication over radio frequency communication and microwave communication. The FSO works in the same way optical fiber cable (OFC) network works with the only difference that the optical beams were transmitted through the free space and not by using the OFC core i.e. the glass fiber. The presence of mist, fog, rain and clouds in the atmosphere directly affects the performance of FSO and the power of propagating signal is degraded significantly. Since the wavelength of propagating beam is comparable to size of fog particles, they mainly lead to atmospheric attenuation. To mitigate the impact of atmospheric attenuation on signals, the present study develops a spectrum slicing (SS)-wavelength division multiplexing (WDM) system with Pre and Post Amplification. The performance of the proposed SS-WDM-Pre and SS-WDM-Post scheme is analyzed and then compared with the traditional SS-WDM model in the Opti-system in terms of Q-factor and BER values. The analysis of the proposed and traditional scheme is done under varying attenuation and power signals during summer, winter, autumn and spring season.The comparative analysis proved that the performance of the proposed SS-WDM-Post and SS-WDM-Pre-model is more effective and efficient when compared with the traditional SS-WDM model in terms of Q-Factor and BER during all 4 seasons.

A high-reliability diffraction-limited atomic iodine photodissociation laser is described. It is shown that a diffraction-limited output beam is obtained when the laser pulse is extracted before the onset of gain-medium inhomogeneities caused by non-uniform deposition of the pump radiation. No degradation of the beam focusability is observed for intensities at which the final amplifier is heavily saturated.

Network planning is an important design-step wherein various network resources are provisioned at different network locations. Traffic demand for all node pairs in the network is an important determining factor for network planning, and typically, a static traffic demand matrix consisting of long-term average traffic values for all node pairs is employed. However, assessment of traffic demand matrix may not be accurate (precise). In this paper, we propose an optimization framework to minimize traffic congestion in a wavelength-routed wavelength-division multiplexing WDM optical backbone network using such approximate traffic demands. Modeling such a network is constrained by limited network resources, and can be formulated in general as a fuzzy optimization problem. Moreover, decision maker might want to relax traffic congestion goal by a small margin in presence of approximate traffic demand matrix, so as to reach some aspiration level, rather missing the crisp target by a very small amount. We use the network planning model to minimize traffic congestion so as to achieve an aspiration level of traffic congestion. We use Zimmermann’s fuzzy programming technique to explore mixed integer linear programing based optimization model incorporating fuzzified constraints and objective function. All related constraints, such as traffic and lightpath routing, wavelength selection, restriction due to average propagation delay, lightpath degree and maximum hop count constraints are taken into consideration. Following the proposed model, under fuzzy environment, we implement reliable and efficient network planning and traffic provisioning, and estimate traffic congestion more accurately.

A novel hybrid multimode interferometer for sensing applications operating with both TE and TM polarizations simultaneously is proposed and numerically demonstrated. The simulations were performed assuming an operating wavelength of 633 nm with the goal of future use as a biosensor, but its applications extend beyond that area and could be adapted for any wavelength or application of interest. By designing the mutimode waveguide core with a low aspect ratio, the confinement characteristics of TE modes and TM modes become very distinct and their interaction with the sample in the sensing area becomes very different as well, resulting in high device sensitivity. In addition, an excitation structure is presented, that allows good control over power distribution between the desired modes while also restricting the power coupled to other undesired modes. This new hybrid TE/TM approach produced a bulk sensitivity per sensor length of 1.798 rad $$\cdot \textrm{RIU}^{-1} \cdot \upmu {\text m}^{-1}$$ and a bulk sensitivity per sensor area of 2.140 rad $$\cdot \textrm{RIU}^{-1} \cdot \upmu {\text m}^{-2}$$ , which represents a much smaller footprint when compared to other MMI sensors, contributing to a higher level of integration, while also opening possibilities for a new range of MMI devices.

In this paper, zinc phthalocyanine (ZnPc) is chosen as the active layer to form a vertical thin film phototransistor with a structure of Cu/ZnPc/Al/ZnPc/ITO. ZnPc has a good photo-sensitive characteristic. Illumination can promote the production of electron–hole pairs, and illumination can reduces the height of the Schottky barrier. When Vbc = 0 V, the barrier height is 0.485 eV under 351 nm light, and the barrier height is 0.509 eV under darkness. It can be concluded that illumination can reduces the barrier height of 0.024 eV in this device.

A self-frequency-locked laser in a 1.55 μm band is demonstrated by adding a segment of samarium-doped fibre (SDF) into an erbium-doped fibre (EDF) ring laser cavity. The narrow band output signal, with a 3 dB down line width of less than 0.15 nm and a side-mode suppression ratio larger than 30 dB, is nearly polarization independent. A multiwavelength EDF ring laser source, using a 1×n synchronous optical switch and n segments of SDF with different lengths, is proposed.