Subset-Optimized Polarization-Multiplexed PSK for Fiber-Optic Communications

A more power-efficient modulation format than polarization-multiplexed quadrature phase-shift keying (PM-QPSK) can be obtained by optimizing the amplitude ratio between symbols with odd and even parity in the PM-QPSK constellation. The optimal amplitude ratio approaches the golden ratio at high signal-to-noise ratio (SNR), yielding a 0.44 dB increase in asymptotic power efficiency compared to PM-QPSK. Union bound expressions are derived for the bit and symbol error rate of the new format, which together with Monte Carlo simulations give the power efficiency at both low and high SNR. A similar optimization performed on PM-8PSK gains 1.25 dB

Airborne laser scanning data estimates for forests that are candidates for thinning cuttings : calculations of volume density

This master’s thesis is a remote sensing study of an area-based method used to detect forest in need of thinning by use of laser data and field samples. Only pine-dominated forest has been included in the study and height limits were set to match empirical restrictions. The study area was in the municipality of Älvsbyn (Latitude 65° 40´ N, Longitude 21° 00´ E), in northern Sweden. The Swedish authority Lantmäteriet is currently laser scanning most parts of Sweden, providing new opportunities and applications. The primary aim of the national laser scanning is to create a new elevation model, useful in consequence analysis of climate changes. The laser data are, therefore, small footprint with 0.5 – 1 returns m-2 and classed into ground, water or unknown. However the opportunity in question is that the same laser data may also be useful for measuring forest, as shown in this study. The use of these laser data may be advantageous for forestry since the data are provided to the public at a low cost. The direction of this study that differs from other laser studies is the use of volume density (in Swedish, “massaslutenhet” ;Skogsord 1983) as a variable to describe the forest. If volume density and height of the forest are known, the basal area and volume can be calculated as well. These connections were founded by Jonsson (1914) and have been used for forest estimation based on aerial photos (Åge 1983). Volume density index may also be a useful variable in deciding whether to thin the forest or not. Raster images of basal area, height, volume density, and volume were created over the study area using estimations based on regression analysis. The accuracy was high inside the field samples and over fitting could be rejected by cross validation. A model using the raster images were created in the program ArcGIS to enable a user to decide what kind of forest to identify for thinning operations. The output from this model was compared and evaluated with an existing stand registry. To summarize, this study manifests that low pulse density laser data can be used successfully to find and measure pine-dominated forest in need of thinning operations. The procedure described in this study may also be useful for detecting thinning for other types of forests as well.

Building up low-complexity spectrally-efficient Terabit superchannels by receiver-side duobinary shaping

Recently, an increasing interest has been put on spectrally-efficient multi-carrier superchannels for beyond 100G. Apart from orthogonal frequency-division multiplexing (OFDM) and Nyquist wavelength-division multiplexing (WDM), another low-complexity WDM approach based on transmitter-side pre-filtering and receiver-side duobinary shaping is proposed to build up multi-carrier superchannels. This approach is referred to as receiver-side duobinary-shaped WDM (RS-DBS-WDM). Generation and transmission of a 1.232-Tbit/s 11-carrier superchannel is experimentally demonstrated. The superchannel signal can be well fit inside the passband of multiple 300-GHz reconfigurable optical add and drop multiplexers (ROADMs). In the superchannel scenario, the proposed RS-DBS-WDM is qualitatively compared with OFDM and Nyquist-WDM in terms of implementation complexity. In sum, the proposed RS-DBS-WDM approach features high transceiver analog-bandwidth efficiency, high spectral-efficiency, the absence of specific spectral manipulation, compatibility with conventional WDM technologies and coherent detection algorithms, and comparable implementation penalty

Comparison of polarization-switched QPSK and polarization-multiplexed QPSK at 30 Gbit/s

We present the first experimental results for polarization-switched QPSK (PS-QPSK) and make a comparison with polarization-multiplexed QPSK. Our measurements confirm the predicted sensitivity advantage of PS-QPSK. We have also studied the single channel performance after transmission over 300 km and support the results with numerical simulations. It is shown that the two modulation formats have similar nonlinear tolerance and that optical dispersion compensation outperforms compensation with digital signal processing in the single channel case. Finally, we propose a novel transmitter for PS-QPSK based on an IQ modulator and two amplitude modulators driven in a push-pull configuration

Modified constant modulus algorithm for polarization-switched QPSK

A modified constant modulus algorithm (CMA) is presented that allows polarization demultiplexing and equalization of polarizationswitched QPSK. An implementation is suggested that allows easy switching between the traditional and the modified CMA. Using numerical simulations, the suggested algorithm is shown to have similar performance as CMA has for polarization-multiplexed QPSK

Frequency and polarization switched QPSK

We propose 8-dimensional biorthogonal modulation as a format with 3 dB increased asymptotic power efficiency over PM-QPSK. We demonstrate one possible experimental implementation of this format based on frequency and polarization switching and compare with dual-carrier PM-QPSK and PS-QPSK

Interleaved Polarization Division Multiplexing in Self-Homodyne Coherent WDM Systems

We demonstrate increased spectral efficiency for self-homodyne coherent WDM systems by using a novel interleaved polarization division multiplexing scheme

Filter Optimization for Self-Homodyne Coherent WDM Systems using Interleaved Polarization Division Multiplexing

We examine the impact of filtering on self-homodyne coherent WDM systems using the interleaved polarization division multiplexing scheme. To investigate the performance limit and to provide more insight into previously obtained experimental results we perform numerical simulations in which different filter shapes and filter bandwidths are used. It is shown that with proper prefiltering of the data and filtering of the pilot tone in the receiver, performance can approach that of an intradyne system, which would make it possible to implement coherent systems with high spectral efficiency without any digital signal processing in the receiver

Transmission of PM-QPSK and PS-QPSK with different fiber span lengths

We perform experimental and numerical investigations of the transmission reach of polarization-switched QPSK (PS-QPSK) and polarization-multiplexed QPSK (PM-QPSK) for three different fiber span lengths: 83, 111 and 136 km. In the experimental comparison we investigate the performance of PS-QPSK at 20 Gbaud and PM-QPSK at the same bit rate (60 Gbit/s) and at the same symbol rate, both the single channel case and a WDM system with 9 channels on a 50 GHz grid. We show that PS-QPSK gives significant benefits in transmission reach for all span lengths. Compared to PM-QPSK, use of PS-QPSK increases the reach with more than 41 % for the same symbol rate and 21 % for the same bit rate. In the numerical simulations we use the same data rates as in the experiment. The simulation results agree well with the experimental findings, but the transmission reach is longer due to the absence of various non-ideal effects and higher back-to-back sensitivity. Apart from using data coded in the absolute phase in the simulations, we also investigate differentially coded PS-QPSK for the first time and compare with PM-QPSK with differential coding. The power efficiency advantage of PS-QPSK then increases with approximately 0.3 dB at a bit error rate of 10-3, resulting in a further relative transmission reach improvement over PM-QPSK. Both the experimental and the numerical results indicate that PS-QPSK has slightly higher tolerance to inter-channel nonlinear crosstalk than PM-QPSK

Prospective life cycle assessment of a flexible all-organic battery

Strong interest from researchers and industry is accelerating development of flexible energy storage technologies for future flexible devices. It is critical to consider the environmental perspective in early development of new emerging technologies. In this study, cradle-to-factory gate prospective life cycle assessment (LCA) was performed on production of an all-organic battery with conductive redox polymers as electrode material. To gain a better understanding of the environmental performance of the all-organic battery, a flexible lithium-ion (Li-ion) battery with lithium titanate oxide and lithium cobalt oxide as electrode active materials was modeled as reference. Main environmental impacts of the all-organic battery were attributable to anode and cathode production, with electrode backbones being the main contributors. Solvents, catalysts, waste treatment, energy, and bromine were key individual contributors. Comparison with the flexible Li-ion battery indicated inferior environmental performance of the all-organic battery due to its relatively low specific energy (Wh/kg) and large amount of materials needed for production of its electrode backbones. Sensitivity analysis showed that changing scaling-up parameters and the production route of 3,4-ethylenedioxythiophene (a precursor of electrode backbones) strongly influenced the results. In order to lower the environmental impacts of the all-organic battery, future research should focus on designing a short production chain with lower material inputs of electrode backbones, increasing battery cycle life, and improving the specific energy of the battery. In addition, relevant recommendations were provided for prospective LCAs of upscaled systems