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The exponential growth of the demand for broadband services has imposed great challenges on the design of spectrum-efficient optical transmission system in Passive Optical Network (PON). Recently, an innovative Orthogonal Frequency Division Multiplexing (OFDM) scheme, called Polar-OFDM (P-OFDM), has emerged as a promising solution to boost the spectral efficiency of optical transmission in PON. However, the traditional P-OFDM does not yet perform best in spectral efficiency as it only uses half of the total subcarriers. In this paper, we verify a promising complementation between Polarization Multiplexing (POLMUX) and P-OFDM aiming at higher spectral efficiency. We then propose the full-subcarriers P-OFDM by loading data on the even-indexed subcarriers of X polarization and the odd-indexed subcarriers of Y polarization, respectively. Thus, all of the subcarriers will be utilized for effective data transmission, which can double the spectral efficiency. More importantly, because the subcarriers are interlaced on different polarizations, the cross-polarization interference can be significantly mitigated, which enables the independent channel estimation and equalization at the receiver to recover the data carried on each polarization. Our evaluation results demonstrate that the proposed system realizes the double spectral efficiency of the traditional P-OFDM with reasonable Bit Error Rate (BER) performance loss. [ABSTRACT FROM AUTHOR]

Abstract: Since atmosphere deeply influences the beams propagated in space-to-ground optical communications, it is important to study its effects on the beam transmission in the atmospheric channel. In this paper, we analyze the impacts of atmospheric channel with the theory of free space optical communication. First, we investigate the atmospheric attenuation of different beams through the mathematical models. Then, we analyze the effects of atmospheric turbulence on the signal transmission by the atmospheric refractive index structure constant. In addition, we simulate the atmospheric transmittance with different zenith angles, beams, heights and rainfall. The results show that the wavelength, atmospheric turbulence, zenith angle, height and rainfall have important impacts on the signal transmission of space-to-ground optical communications. This demonstrates much theoretical significance on the wavelength selection, height settings of the optical ground station as well as angle selection of transmitter. [Copyright &y& Elsevier]

Abstract: Saving the electrical requirements of network operators around the world makes power costs show a continuously decreasing trend. However, reducing the power costs is not only one way of gaining the marginal profit, a network operator also needs providing high-level quality of service (QoS), as well as employs effective strategies of pricing and hybrid grooming (i.e., integration of traffic grooming with an optical bypass) to make more users wish to pay the expense for their applications. In the final, users enjoy their services meanwhile operators obtain high profit in a power-efficient way, i.e., “double-win”. Accordingly, we propose the fast sub-optimal heuristics including Single-hop and Power-efficient Grooming algorithm based on Game theory (SPG2) as well as Multi-hop and Power-efficient Grooming algorithm based on Game theory (MPG2). Simulation results demonstrate that, compared with SPG2, MPG2 has the better comprehensive performance of both power efficiency and double-win between user and network operator in IP over WDM networks. [Copyright &y& Elsevier]

Abstract: Optical communication technology shows promising prospects to fulfill the large bandwidth requirements of future deep-space exploration. This paper mainly studies the link design of Moon-to-Earth optical communication based on the telescope array receiver. Firstly, we analyze and design the telescope array model. An array of relatively small-sized telescope combined to form a larger synthesized aperture is a viable and efficient alternative to a large monolithic telescope. Moreover, this array structure also saves the total costs of the telescopes. In addition, we present an end-to-end system analysis to provide the expected signal and background photons as a function of the Moon–Earth distance. Then, we describe the work on the link design of the Moon-to-Earth optical communication. This primarily includes the received power, the antenna gain, the space loss, the atmospheric loss, and so on. We also provide an approximation calculation to the channel capacity, the data rate, the bit error ratio (BER) and signal-to-noise ratio (SNR). This demonstrates much theoretical significance on the actual Moon-to-Earth optical communication. [Copyright &y& Elsevier]

Abstract: With the network size increasing, the optical backbone is divided into multiple domains and each domain has its own network operator and management policy. At the same time, the failures in optical network may lead to a huge data loss since each wavelength carries a lot of traffic. Therefore, the survivability in multi-domain optical network is very important. However, existing survivable algorithms can achieve only the unilateral optimization for profit of either users or network operators. Then, they cannot well find the double-win optimal solution with considering economic factors for both users and network operators. Thus, in this paper we develop the multi-domain network model with involving multiple Quality of Service (QoS) parameters. After presenting the link evaluation approach based on fuzzy mathematics, we propose the game model to find the optimal solution to maximize the user’s utility, the network operator’s utility, and the joint utility of user and network operator. Since the problem of finding double-win optimal solution is NP-complete, we propose two new hybrid protection algorithms, Intra-domain Sub-path Protection (ISP) algorithm and Inter-domain End-to-end Protection (IEP) algorithm. In ISP and IEP, the hybrid protection means that the intelligent algorithm based on Bacterial Colony Optimization (BCO) and the heuristic algorithm are used to solve the survivability in intra-domain routing and inter-domain routing, respectively. Simulation results show that ISP and IEP have the similar comprehensive utility. In addition, ISP has better resource utilization efficiency, lower blocking probability, and higher network operator’s utility, while IEP has better user’s utility. [Copyright &y& Elsevier]