Low-noise Pr3+-doped fluoride fibre amplifier

The authors have constructed a Pr³⁺-doped fluoride amplifier (PDFA) module pumped by an Nd-YLF laser. The maximum signal gain and noise figure were 20 dB and 5 dB respectively. An output power of 19.2 dBm was achieved at an input signal power of 11.0 dBm. It was confirmed that this PDFA module has low-noise characteristics from experimental results on its use in a subcarrier multiplexed multichannel AM-VSB video signal transmission     

Low-noise and high-power Pr3+-doped fluoride fiberamplifier

We have successfully developed a low-noise and high-power Pr³⁺-doped fluoride amplifier (PDFA) module with a cascade configuration. The maximum signal gain and noise figure were 40.6 dB and 5 dB, respectively. An output power of 20.1 dBm was achieved at an input signal power of 0 dBm. We confirm that this PDFA module performs well from experimental results on its use in a 40 channel AM-VSB video signal transmission and a 10 Gbit/s digital transmission     

Development of an efficient praseodymium-doped fiber amplifier

This paper describes the development of an efficient praseodymium-doped fluoride fiber amplifier (PDFA) using newly developed PbF₂-InF₃-based fluoride single-mode fiber. First, the spectroscopic properties of Pr³⁺ in PbF₂-InF ₃-based and ZrF₄-based fluoride glass are compared and then the fabrication of high-NA PbF₂-InF₃-based fluoride single-mode fiber is presented. The gain coefficients obtained with the developed fiber are 0.36 dB/mW with a forward pumping scheme and 0.4 dB/mW with a bidirectional pumping scheme. We use this newly developed fiber to construct two types of an efficient PDFA module. We realized a 19-in rack size PDFA module with a master oscillator/power amplifier laser diode (MOPA-LD) and a plug-in type PDFA module with a wavelength-stabilized 1.017-μm LD and describe their amplification characteristics     

Efficient PDFA module using high-NA PbF/sub 2//InF/sub 3/-based fluoride fiber

The highest reported single-pass gain coefficient of 0.36 dB/mW has been achieved using a newly developed Pr/sup 3+/-doped high-NA PbF/sub 2//InF/sub 3/-based fluoride fiber, with a /spl Delta/n of 6.6%, a core diameter of 1.2 /spl mu/m and a transmission loss of 250 dB/km at 1.2 /spl mu/m. This fiber was used to construct an efficient PDFA module with a MOPA-LD. A small-signal net gain of 22.5 dB was achieved at 1.30 /spl mu/m with a pump power of 23m mW.     

Plug-in type 1.3-/spl mu/m fiber amplifier module for rack-mounted shelves

We have successfully developed a plug-in type PDFA module for rack mounted shelves which is assembled on a printed-board. In this module, we use a newly developed Pr/sup 3+/-doped high-NA PbF/sub 2//InF/sub 3/-based fluoride fiber and wavelength stabilized 1.017-/spl mu/m laser diodes (LDs). We have obtained a small-signal gain of 24 dB and a noise figure of 6.6 dB at 1.30 /spl mu/m with an LD drive current of 240 mA/spl times/2. We achieved an output power of 10 dBm with a signal input power of 0 dBm. The total power consumption of this module, including that of a Peltier cooler, was 3.5 W when the LD drive current was 240 mA/spl times/2.     

28.3 dB gain 1.3 μm-band Pr-doped fluoride fiber amplifiermodule pumped by 1.017 μm InGaAs-LD's

A praseodymium (Pr)-doped fluoride fiber amplifier (PDFA) module that is pumped by strained quantum-well InGaAs laser diodes (LDs) is described. The amplifier module, consisting of a four LD pump configuration and a high NA Pr-doped fluoride fiber with low scattering loss, exhibits a maximum signal gain of 28.3 dB and a saturation output power of 6 dBm at a signal wavelength of 1.30 μm. It is shown to be the most promising module for the 1.3-μm-band optical amplifier     

Pr/sup 3+/-doped fluoride fiber amplifier module pumped by a fiber coupled master oscillator/power amplifier laser diode

We constructed the first Pr/sup 3+/-doped fluoride fiber amplifier (PDFA) module pumped by a fiber-coupled master oscillator/power amplifier laser diode (MOPA-LD) operating at 1.017 /spl mu/m. The maximum signal gain and noise figure were 30.5 and 5.5 dB, respectively. An output power of 18 dBm was achieved at an input signal power of 0 dBm. Furthermore, we showed that the use of MOPA-LD pumping, rather than conventional Nd-YLF laser pumping, makes it possible to halve the length of the Pr/sup 3+/-doped fluoride required in the amplifier module and also allows a broader spectral bandwidth to be achieved.     

Direct fibre-optic transmission of entire microwave satellite antenna signals

The entire 500 MHz bandwidth multicarrier C-band microwave signal spectrum from a satellite antenna is transmitted over low-loss optical fibre. The optical system introduces 1dB or less of degradation for both low-spectral-density QPSK signals and high-spectral-density FM video signals present in typical satellite transmission systems. For the video signals, the signal/noise ratio after AM conversion was reduced from 56 dB to 55dB.     

Performance of Pr-doped fluoride fibre amplifier for multichannel AM-VSB transmission

The system performance of a Pr-doped fluoride fibre amplifier was examined for multichannel AM-VSB video signal transmission for the first time. For a CNR of 51 dB, a loss budget of 15.1 dB was obtained with the amplifier, and for a CNR of 46 dB, the loss budget was expanded to 20.1 dB.<>     

基于3D混合树和视觉特性的视频可分级编码算法

分析了视频数据的3D小波系数分布特性,提出了一种基于混合3D树型结构和HVS特性的视频可分级编码算法.首先,依据小波低、高频系数的自相关性,确定相应的树型结构来扫描和处理时间维上的低、高频系数,明显减少了用于定位重要系数的同步信息;其次,依据人类视觉系统对各频率子带敏感程度的不同,对各子带系数进行加权,使得重构视频的重要系数得以排在码流前端,从而在很大程度上提高了中低码率下视频的重构质量.对多种标准测试视频的仿真实验验证了本文算法的有效性,与非对称树型结构编码方案和单一时空方向树结构方案相比,该算法解码图像的Y、U和V 3个分量的均峰值信噪比分别高出0.65dB、1.75dB、1.77dB和0.23dB、2.11dB、1.72dB.此外,算法有效抑制了振铃效应,并获得了更好的主观效果.     

Video transmission over cabled monomode fibre at 1.523 ?m using PFM with 2-PSK heterodyne detection

625-line colour video transmission over 61 km of cabled monomode fibre at 1.523 ?m is reported. PFM with 2-PSK heterodyne detection gives a receiver sensitivity of ?53.4 dBm at 50 dB video SNR, which is 5.2 dB from the shot noise limit and 8.4 dB better than direct detection. Alternative modulation configurations are discussed.     

A 980-nm band laser diode pump source with a detuned wavelength of1000 nm for praseodymium-doped fiber amplifiers

By using practical high-power 980-nm band laser diodes, efficient direct pumping for a praseodymium-doped fiber amplifier (PDFA) is achieved. The lasing wavelength is detuned from 980 to 1000 nm by selective optical feedback from a fiber grating     

Linearization of Multichannel Analog Optical Transmitters by Quasi-Feedforward Compensation Technique

A quasi-feedforward compensation technique is described for linearization of LED's in analog fiber optics based video transmission systems, Experimentally we have observed an improvement of more than 35 dB in second-order and 20 dB in third-order distortion in a system transmitting three TV channels simultaneously. The linearized system is capable of video signal transmission over a distance of at least 2 km without repeaters.     

Multichannel AM video transmission using a high-power Nd:YAG laserand linearized external modulator

A high-power Nd:YAG laser with a linearized external modulator-based system is demonstrated for a transmission of 50 channels of vestigal sideband amplitude modulated (VSM AM) video. The 1320-nm diode-pumped Nd:YAG laser is an attractive source for AM video transmission due to the high output power (~200 mW) and low relative intensity noise (<-170 dB/Hz). However, the required external modulator generates third-order distortion products, which limit the performance of such a system. A predistortion linearization technique is described. It reduces the modulator generated third-order distortion products by 16.4 dB, allowing a modulation index of 3.37% per channel. When combined with the Nd:YAG laser, this yields a 50-channel video transmission system with a 12 dB optical power budget for video carrier-to-noise ratios of 52 dB and composite distortion products (CSO and CTB) of less than -60 dBc. The demonstrated power budget is sufficient to allow four-way power splitting, with the remaining margin comparable to the test results obtained with DFB (distributed-feedback) laser-based AM transmission systems     

Cross‐layer 1 and 5 user grouping/power allocation/subcarrier allocations for downlink OFDMA/NOMA video communications

Wang et al proposed cross‐layer resource allocation for orthogonal frequency division multiple access (OFDMA) video transmission systems. Unlike Wang et al, we add non‐orthogonal multiple access (NOMA) to the downlink OFDMA video transmission system and propose power allocation for users on each subcarrier (cluster) to minimize sum of video mean square error (MSE) to increase the peak signal‐to‐noise ratio (PSNR), the video quality. For OFDMA/NOMA video communication systems, we propose cross‐layer user clustering to reassign the subcarriers based on sum video distortion minimization and derive the optimal power allocation among NOMA users on the same subcarrier to minimize the sum video distortion. Numerical results show that the proposed scheme outperforms the previous OFDMA cross‐layer scheme by Wang et al by 2.2 to 4.5 dB in PSNR and previous OFDMA NOMA physical layer scheme by Ali et al by 2 to 4.4 dB in PSNR, when SNR = 15 dB, and the number of users is 6 to 12.     

Multichannel AM-VSB television signal transmission using anerbium-doped optical fiber power amplifier

The use of an erbium-doped optical fiber power amplifier in a multichannel amplitude-modulated vestigial-sideband CATV transmission system for potential subscriber loop applications is discussed. Using a color-center laser pump at 1.48 μm, a fiber-to-fiber gain of 11.5 dB (at 1.539 μm), which is 10 dB compressed from the small-signal gain, and a total system power margin of 15 dB were achieved. No intermodulation distortion was introduced by the fiber amplifier. The received video SNR of 40-46 dB was limited by the linearity of the distributed-feedback laser diode used     

Broadband video distribution over passive optical network using subcarrier multiplexing techniques

A 16-channel subcarrier-multiplexed video system has been optimised for operation over a passively split optical network. The system delivers a weighted SNR of 47 dB with an optical power budget of 34 dB and a dynamic range of 19 dB.<>     

Unrepeatered video transmission using pulse frequency modulation over 100 km of monomode optical fibre

Unrepeatered transmission of 625-line colour video signals using PFM over monomode optical fibre is reported. The results show that a received video signal/noise ratio better than 53 dB unified weighted was achieved over 68 km of fibre at 1.3 ?m and 102 km at 1.52 ?m.     

Analogue video transmission over cabled monomode fibre using optical frequency modulation with heterodyne detection

The design and receiver sensitivity of a heterodyne detection system using analogue optical frequency modulation is examined for the transmission of a single baseband colour video signal. After transmission over 30 km of cabled monomode fibre, receiver sensitivity was measured to be ?70.3 dBm for a 53 dB unified weighted video SNR.     

Laser based WDM multichannel video transmission system

The results of a WDM experiment involving the transmission of three video channels using AM-VSB modulation on each of three lasers in the 800?900 nm range are presented. A weighted video signal/noise ratio greater than 40 dB was achieved at each wavelength for a laser modulation index of 0.3 over a 1.1 km link.