Self-Seeded RSOA-Fiber Cavity Lasers vs. ASE Spectrum-Sliced or Externally Seeded Transmitters—A Comparative Study

Reflective semiconductor optical amplifier fiber cavity lasers (RSOA-FCLs) are appealing, colorless, self-seeded, self-tuning and cost-efficient upstream transmitters. They are of interest for wavelength division multiplexed passive optical networks (WDM-PONs) based links. In this paper, we compare RSOA-FCLs with alternative colorless sources, namely the amplified spontaneous emission (ASE) spectrum-sliced and the externally seeded RSOAs. We compare the differences in output power, signal-to-noise ratio (SNR), relative intensity noise (RIN), frequency response and transmission characteristics of these three sources. It is shown that an RSOA-FCL offers a higher output power over an ASE spectrum-sliced source with SNR, RIN and frequency response characteristics halfway between an ASE spectrum-sliced and a more expensive externally seeded RSOA. The results show that the RSOA-FCL is a cost-efficient WDM-PON upstream source, borrowing simplicity and cost-efficiency from ASE spectrum slicing with characteristics that are, in many instances, good enough to perform short-haul transmission. To substantiate our statement and to quantitatively compare the potential of the three schemes, we perform data transmission experiments at 5 and 10 Gbit/s

Ultra-Fast Beam Steering for Next Generation Mobile Communication

Nowadays, end users consume more data on mobile devices, such as smartphones, tablets or laptops, than on fixed-wired computers. Simultaneously, the quantity of data per session increases tremendously, primarily driven by video-on-demand and teleconferencing services. To cope with the increasing demand, new wireless communication schemes and technologies are needed. To increase the capacity of mobile networks by the required order of magnitudes, two major technological changes can be implemented. First, the channel capacity can be increased by driving communication systems at millimeter waves. Second, the aggregated cell capacity can be increased by implementing space division multiplexing. In both cases, these new concepts require faster, more compact, and cheaper hardware solutions. In this work, the technical challenges resulting from the implementation of both aforementioned solutions are solved by using photonics in place of electronics. In addition, the photonic-based implementation presented in this work empowers a novel multiplexing scheme, which leverages ultra-fast beam steering. This development, not available with electronic components, provides at the same time multi-beam capacity and reduces the hardware requirements

Flow boiling of R-245fa at high saturation temperature

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Flow boiling heat transfer in minichannels at high saturation temperatures: Part II: Assessment of predictive methods and impact of flow regimes

International audienceIn order to evaluate the reliability of the current flow boiling heat transfer prediction methods for conditions of high saturation temperatures, this paper focuses on the comparison between experimental results (presented in the first part of this two-part article) and results predicted with the commonly used correlations or models from the literature. The dataset was obtained with R-245fa as working fluid in a 3.00 mm inner diameter stainless steel tube. It is characterized by a saturation temperature ranging from 60 °C to 120 °C. The database is composed of 5964 data points covering four flow patterns: (i) intermittent flow, (ii) annular flow, (iii) dryout flow, and (iv) mist flow regimes. An extensive literature review was performed to select the flow boiling heat transfer prediction methods that were classified according to their theoretical background. Finally, thirty flow boiling prediction methods were assessed against our database. The results are presented graphically but also statistically. The effect of the saturation temperature and the kind of flow pattern on the ability of the methods to predict the flow boiling heat transfer coefficient were investigated. At 60 °C, most of the prediction methods produce homogeneous results and are able to predict with accuracy the flow boiling heat transfer coefficient. On the contrary at 120 °C, the existing methods fail to predict the heat transfer coefficient with accuracy. The only methods able to capture the experimental trends are those developed from carbon dioxide data with or without other fluids

Bit-and power-loading-A comparative study on maximizing the capacity of RSOA based colorless DMT transmitters

We present a comparative study of the capacity increase brought by bit- and power-loading discrete multi-tone (DMT) modulation for low-cost colorless transmitters. Three interesting reflective semiconductor optical amplifier (RSOA) based colorless transmitter configurations are compared: First, an amplified spontaneous emission (ASE) spectrum-sliced source; second, a self-seeded RSOA fiber cavity laser (FCL) and third, an externally seeded RSOA. With bit- and power-loaded DMT, we report record high line rates of 6.25, 20.1 and 30.7 Gbit/s and line rates of 4.17, 10.1 and 24.5 Gbit/s in a back-to-back and in a 25 km nonzero dispersion shifted fiber (NZDSF) transmission experiments for the three transmitter configurations, respectively. In all the experiments, BER (bit error ratios) below an FEC (forward error correction) limit of 7.5 × 10−3 were achieved.ISSN:2076-341

Optical Transmitters without Driver Amplifiers—Optimal Operation Conditions

ISSN:2076-341

Optical Transmitters without Driver Amplifiers—Optimal Operation Conditions

An important challenge in optical communications is the generation of highest-quality waveforms with a Mach–Zehnder modulator with a limited electrical swing (Vpp). For this, we discuss, under limited Vpp, the influence of the waveform design on the root-mean-square amplitude, and thus, the optical signal quality. We discuss the influence of the pulse shape, clipping, and digital pre-distortion on the signal quality after the electrical-to-optical conversion. Our simulations and experiments, e.g., suggest that pre-distortion comes at the expense of electrical swing of the eye-opening and results in a lower optical signal-to-noise ratio (OSNR). Conversely, digital post-distortion provides operation with larger eye-openings, and therefore, provides an SNR increase of at least 0.5 dB. Furthermore, we find that increasing the roll-off factor increases the electrical swing of the eye-opening. However, there is negligible benefit of increasing the roll-off factor of square-root-raised-cosine pulse shaped signals beyond 0.4. The findings are of interest for single-channel intensity modulation and direct detection (IM/DD) links, as well as optical coherent communication links

Modeling of a Microchannel Evaporator for Space Electronics Cooling : Entropy Generation Minimization Approach

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