FBG-based bidirectional optical cross connects for bidirectional WDM ring networks

This paper proposes a new bidirectional optical cross connect (BOXC) using fiber Bragg gratings (FBGs) and optical circulators for bidirectional wavelength-division-multiplexing ring networks. Dynamic and independent wavelength routing is achieved by employing cascaded tunable FBGs. The proposed BOXC requires a small tuning range equal to wavelength channel spacing for tunable FBGs. Therefore, the wavelength count of the proposed BOXC could be increased easily without imposing constraint on the tuning range of FBGs. Coherent and incoherent crosstalk arising in the proposed BOXC and their impact on the power penalty are studied in detail. The Monte Carlo simulation is used to characterize the probability distribution of the power penalty due to both coherent and incoherent crosstalk under various conditions. The specification requirements are then obtained for the FBGs used in BOXC nodes with a different number of wavelengths. The study in this paper reveals that the requirement for the isolation of FBGs is more stringent than that for the reflectivity of FBGs at the Bragg wavelength. It is also shown that a large BOXC can be built based on the Benes network structure, and a method to reduce the complexity is also presented.     

Bidirectional optical fiber transmission systems using Ramanamplification

Bidirectional optical fiber transmission systems using Raman amplification are discussed. Analytical expressions for signals amplified by both forward and backward Raman scattering are presented. It is found that there exists an optimal pump power for the maximum unrepeated transmission length in a bidirectional system and that the maximum length is about 450 km, which is about the same as that of the unidirectional system     

Bidirectional optical transmission using polarised light waves

Bidirectional optical transmission using polarised light waves is demonstrated for the first time. Transmission of 100 Mbit/s signals over 13.6 km of polarisation-maintaining fibre occurs simultaneously in both directions at 1.55/?m. LD transmitters with polarisation-maintaining fibre pigtails, polarisation-maintaining fibre couplers, fibre polarisers and Ge-APD receivers are used.     

Bidirectional WDM passive optical network for simultaneous transmission of data and digital broadcast video service

We have demonstrated an easily upgradable bidirectional passive optical network for the simultaneous transmission of wavelength-division-multiplexing channels and digital broadcast video signals. The proposed network could transmit 15 2.5-Gb/s downstream channels, 15 155-Mb/s upstream channels, and one broadcast signal consisting of more than 70 digital video channels.     

Bidirectional analogue optical transmission using semiconductor junction transceivers

The use of a Burrus l.e.d. as both photoemitter and photodetector in a continuously bidirectional analogue communications link is experimentally investigated. Such a system appears capable of operating at sampling rates below 100 kHz over links with about 5 dB loss to provide a signal/noise ratio of 50 dB.     

Subcarrier multiplexed transmission using wavelength division multiplexing and optical amplifier

Measured bit-error-rate performance is reported for a wavelength-division-multiplexed subcarrier-multiplexed transmission experiment. Six digital channels were carried over two wavelengths in the 1.5 mu m wavelength region and amplified using a semiconductor laser amplifier which gave a 12 dB increase in tolerable path loss with no noticeable penalty.<>     

Bidirectional and simultaneous transmission of baseband and wireless signals over RSOA based WDM radio-over-fiber passive optical network using incoherent light injection technique

Reflective semiconductor optical amplifier (RSOA) based wavelength division multiplexed radio-over-fiber passive optical network (WDM−RoF−PON) has been proposed and demonstrated, to transmit 2.5 Gbps baseband (BB) and 1.25 Gbps wireless data in downstream and 1 Gbps BB data signal in upstream over 25-km single-mode fiber (SMF), and wireless downstream signal over 25-km SMF as well as 5.2 m free space in air. In the downstream, 2.5 Gbps BB data and 1.25 Gbps wireless data are modulated using single-electrode Mach–Zehnder modulator (SD-MZM) based on double-sideband with optical carrier suppression (DSBCS) scheme and simultaneously transmitted by incoherent light injection technique and employing fiber Bragg grating (FBG) at the base station. RSOA is utilized at the user end to reuse the carrier for uplink transmission. High receiver sensitivity, low bit-error-rate (BER) and excellent eye-diagram, eye height are achieved in our proposed network system and the results affirm the acceptability of proposed RSOA based WDM−RoF−PON.     

WDM upgrading of an installed submarine optical amplifier system

This paper describes the WDM upgrading of a submarine optical amplifier system installed for single-channel transmission in commercial use. The key technologies used include 10-Gb/s high-speed forward error correction, preemphasis to overcome the optical passband-width constraint, optimized signal pulse format that leads to partial return-to-zero (PRZ) signaling, and dispersion compensation to suppress the degradation caused by fiber nonlinearity and dispersion. It also reports field experimental results on upgraded system performance. The results confirm that simply upgrading the terminal equipment allows the transmission capacity of a submersed line consisting of submarine repeaters and cables to be flexibly increased from 10 Gb/s to 40 Gb/s per fiber pair     

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     

A novel hybrid WDM/SCM-PON sharing wavelength for up- and down-link using reflective semiconductor optical amplifier

A hybrid wavelength-division multiplexed/subcarrier multiplexed passive optical network (WDM/SCM-PON) which shares the same wavelength both up-link and down-link is presented by using a reflective semiconductor optical amplifier (RSOA) as a modulator. We investigated down-link of 622 Mb/s using distributed feedback laser diode with direct modulation and 100-Mb/s up-link using an RSOA as a modulator with 900-MHz SCM signal. In our scheme, a novel efficient and cost-effective WDM/SCM-PON using the same wavelength for down/up-link at each optical network unit is proposed and experimentally demonstrated.     

Wavelength reused upstream transmission scheme for WDM passive optical networks

A novel technique facilitating wavelength reused upstream transmission in a WDM passive optical network, eliminating wavelength source at ONUs, is proposed and experimentally demonstrated. A subcarrier frequency is used for downstream transmission and the pure optical carrier is filtered and reused for upstream transmission. The scheme requires only simple baseband receivers at both ONU and OLT terminals.     

波分复用传输系统中EDFA-BDE模块的仿真研究

本文在ＣＯＭＤＩＳＣＯ信号处理工作系统中研究了用于波分复用传输系统的掺铒光纤放大器块图编辑器仿真模块。仿真模块考虑了前向及后向放大的自发辐射噪声。通过信息计算ＥＤＦＡ－ＢＤＥ模块,优化设计了掺铒光纤的长度。在含８级ＥＤＦＡ的ＷＤＭ光传输系统的仿真中论证了模块的实际应用。本文在输出信号幅度及ＡＳＥ噪声谱上都获得了与前期发表的实验相一致的仿真结果,证明了ＥＤＦＡ－ＢＤＥ模块在高饱和状态下的实际可用性。     

1×2 optical switch for WDM transmission systems

A 1×2 optical switch, which also functions as wavelength demultiplexer, is designed and experimentally fabricated utilising a phase plate and a twisted nematic liquid crystal. Measured insertion loss, crosstalk attenuation, and transit time are <1.5 dB, >17.6 dB, and <80 ms, respectively     

1.3 ?m bidirectional optical transmission over 31 km of installed single-mode fibre using optical couplers

Results are reported of 1.3 ?m bidirectional optical transmission over 31 km of installed cabled fibre at transmission rates of 34?650 Mbit/s using fused biconical tapered couplers manufactured at BTRL. With the introduction of 6 dB extra path loss it is possible to double the system capacity incurring only a small additional penalty at 34 and 140 Mbit/s and no other penalty at 320 and 650 Mbit/s.     

5 Gbit/s optical transmission terminal equipment using forwarderror correcting code and optical amplifier

Using forward error correction (FEC) technology and erbium-doped fibre amplifiers (EDFAs), 5 Gbit/s optical transmission terminal equipment provides better than -40 dBm receiver sensitivity at a BER of 10^-11. The experiments focused on the FEC feature of the removal of the BER floor together with long-distance repeaterless transmission     

High-bit-rate bidirectional optical transmission with twosemiconductor laser amplifiers

The authors report a bidirectional transmission carried out with two semiconductor laser amplifiers (SLAs) used alternately as a modulator and a photodetector. Error free transmission is achieved up to 622 Mbit/s     

Full bidirectional fiber transmission using coherence-modulatedlightwaves

A method for simultaneous transmission in both directions of a single fiber is demonstrated utilizing a single source. A high optical isolation of the two counterpropagating signals is obtained by combining coherence modulation in one direction with intensity modulation in the other direction. This allows full duplex transmissions with a single source of signals with identical modulation speed in the two directions     

Distributed amplifier signal shaping strategy for multigigabit digital optical transmission

A novel technique is presented for using the distributed amplifier (DA) as an active pulse shaping/filtering network by effectively constructing a transversal filter. This technique is versatile, and judicious selection of the effective stage delays and gains allows a variety of filtering functions to be implemented. The capability of the technique is illustrated with reference to a GaAs MMIC design for 10 Gbit/s.<>     

Coherent optical tapping using semiconductor optical amplifier

Semiconductor optical amplifiers are attractive not only as optical repeaters but also as functional devices, since carrier density modulation in amplifiers causes a nonlinear phenomenon. Utilizing the effect of the carrier density modulation on the semiconductor optical amplifier junction voltage, a coherent optical tapping is proposed for signal monitoring or control signal extraction. A 155 Mb/s FSK (frequency shift keying) signal tapping was realized with a simple configuration using heterodyne single-filter detection with -24.4 dBm sensitivity. Many applications for this coherent optical tapping are discussed, and basic characteristics for frequency-selective tapping from FDM (frequency division multiplexing) signals and optical amplifier gain control are examined     

Performance of WDM fiber-radio network using distributed Raman amplifier

We investigate the impairment induced by stimulated Brillouin scattering (SBS) effect and noise characteristics of wavelength-division-multiplexing fiber-radio network assisted by distributed Raman amplifier (DRA) or erbium-doped fiber amplifier. Experimental results indicate that forward-pumping DRA can increase the link optical output power limited by SBS effect in downstream transmission and backward-pumping DRA can improve signal-to-noise ratio in upstream transmission, which is verified by binary phase-shift keying transmission experiments. Moreover, our experimental results show that DRA does not introduce additional impairment from interchannel crosstalk due to cross-phase modulation and degradation in spur-free dynamic range.