No abstract

In this paper, we demonstrate the direct modulation and direct detection of 28-Gb/s duobinary signal for the future downstream capacity upgrade in next generation passive optical network (PON). Commercial 10-GHz directly modulated laser (DML) and PIN with a combined modulation bandwidth of ~7 GHz are used as transmitter and receiver respectively. In order to mitigate the chromatic dispersion induced signal distortion, an optical delay interferometer (DI) is employed to narrow down the signal spectrum, thereby realizing 40-km single mode fiber (SMF) transmission in C-band. Besides, the chirp-induced spectral broadening of the directly modulated signal enables a higher launch power than external modulation schemes, which increases the loss budget of the system. As a result, 31-dB loss budget is achieved, supporting 64 users with 40-km reach. Also, as the transceivers in both optical line terminal (OLT) and optical network unit (ONU) are commercial l0-GHz devices, the proposed scheme is compatible with 40-Gb/s time and wavelength division multiplexing passive optical network (TWDM-PON) systems, providing a cost-efficient alternative for the development of 100G PON.

No abstract

Time-and wavelength-division multiplexed passive optical network (TWDM-PON) has been selected by full service access networks as a primary solution for next generation PON stage 2 in April 2012. In this letter, we propose and demonstrate a symmetric 40-Gb/s TWDM-PON with 39-dB power budget. A reflective semiconductor optical amplifier is used in optical network unit as a pre-amplifier to enhance the sensitivity of downstream signals. For the upstream direction, a thermallytuned directly modulated laser with 10-Gb/s modulation rate is used as upstream colorless source, and a chirp management filter is employed in optical line terminal to mitigate chromatic dispersion therefore enabling fiber transmission. Symmetric 40-Gb/s TWDM-PON is experimentally demonstrated with a power budget of 39 dB, which could support 25-km fiber transmission and 1:1000 splitting ratio.

The effective integration of multiple functions into electromagnetic waveabsorbing (EWA) materials is the future development direction but remains a huge challenge. A rational selection of components and the design of structures can make the material have excellent EWA performance and heat dissipation. Herein, the core−shell structured boron nitride@nitrogen-doped carbon (BN@NC) is prepared by using waterborne polyurethane (WPU) as the carbon source via a facile pyrolysis treatment process, where NC is used as the conductive loss shell, and BN serves as an impedance matching core and dominant heat transfer media. As a result, the BN@NC-900 filled with paraffin wax yields a minimum reflection loss of −42.2 dB at 2.2 mm and an effective absorbing bandwidth of 4.48 GHz at 1.8 mm, and its thermal conductivity reaches up to 0.92 W/m•K in epoxy resin. Most importantly, flexible BN@NC/WPU films are prepared and simultaneously achieve the dual-functional capability of efficiently dissipating heat and electromagnetic waves (−50.0 dB). Besides, an attractive multiband absorption feature (>99%) from C to Ku bands is realized and a strong absorbing over −27.0 dB at the S band (2.88 GHz) is even achieved. This study may pave a new route for the rational design of multifunctional EWA materials.

The exploitation of offshore wind power has increased rapidly in recent years. To gain more wind power energy, offshore wind farms move farther from onshore. A comparison between HVAC and HVDC in terms of reliability, cost and transmission capability shows that HVDC is more suitable for long-distance, high-capacity bulk power transmission. However, the HVDC transmission for offshore wind power also faces great challenges because the offshore applications bring critical demands for low volume and low weight for the converters at the offshore side. On the other hand, the new topologies and conversion techniques of power electronic converters expedite many new DC transmission architectures for offshore wind power. Different HVDC architectures by using centralised voltage source converter (VSC), diode rectifier (DR), series-connected wind turbine converters and all-DC wind farm based on DC transformers are reviewed and compared. The advantages, challenges and development and application prospects for various DC transmission solutions are discussed.

High speed data modulation based on bandwidth limited devices has been considered as a cost-effective way to upgrade 10G-EPON to the next generation 100G-EPON. In this paper, we experimentally demonstrate the modulation, fiber transmission and reception of 25-Gb/s signal based on directly modulated laser and photo-detector both operating at 10 GHz. Instead of digital signal processing, the chirp management, dispersion compensation and frequency equalization in our scheme are realized in optical domain using a single delay interferometer. Three popular formats are investigated, including NRZ-OOK, PAM-4 and duobinary. According to the experimental results, the NRZ-OOK format shows its superiority in both launch power and receiver sensitivity, which provides a cost-effective solution for the construction of 100-Gb/s TWDM-PON.

No abstract