Design and Application of Multimode Substrate Integrated Waveguides in Parallel Multichannel Signaling Systems

Multimode signal transmission concept is employed in this paper to increase the channel capacity of a substrate integrated waveguide (SIW) interconnect. In order to generate two uncoupled channels without adding an additional physical link, ${rm TE}_{10}$ and ${rm TE}_{20}$ modes of an SIW interconnect are harnessed as signal carriers. To excite these two orthogonal modes simultaneously, a multimode double launcher is proposed and characterized. It is shown that the performance of the launcher is limited by the coupling between the two mode launchers (transitions). Therefore, a method for improving port isolation is suggested, which results in increasing the channel bandwidths. A balun structure based on an SIW is presented and included in the multimode waveguide in order to efficiently excite the ${rm TE}_{20}$ mode. Ultimately, the multimode waveguide with the optimized transitions is used in a parallel data transmission system demonstrating excellent transmission quality for the data rate of a 1-Gb/s/channel.      

OSNR Monitoring Method for OOK and DPSK Based on Optical Delay Interferometer

We describe a simple method to measure the optical signal-to-noise ratio (OSNR) of on-off-keying (OOK) and differential phase-shift-keying (DPSK) signals by using an optical delay interferometer (ODI) having a sinusoidal and tunable passband. This OSNR monitoring method is independent of chromatic dispersion, polarization-mode dispersion, and noise polarization. We show experimentally that accurate OSNR measurements are made for a 10-Gb/s OOK signal by using a 1-bit ODI and a 40-Gb/s DPSK signal by using a partial-bit ODI with the OSNR ranging from 5 to 25 dB.     

Numerical analysis of four-wave-mixing based multichannel wavelength conversion techniques in fibers

We numerically investigate four-wave-mixing (FWM) based multichannel wavelength conversion for amplitude-modulated signals, phase-modulated signals, together with mixed amplitude and phase modulated signals. This paper also discusses the influence of stimulated Brillouin scattering (SBS) effects on high-efficiency FWM-based wavelength conversion applications. Our simulation results show that DPSK signals are more suitable for FWM-based multichannel wavelength conversion because the OOK signals will suffer from the inevitable datapattern-dependent pump depletion. In future applications, when the modulation format is partially upgraded from OOK to DPSK, the influence of OOK signals on the updated DPSK signals must be considered when using multichannel wavelength conversion. This influence becomes severe with the increase of OOK channel number. It can be concluded that DPSK signals are more appropriate for both transmission and multichannel wavelength conversion,especially in long haul and high bit-rate system.     

基于光纤中四波混频效应的多信道波长转换性能的数值分析

高效多信道波长转换技术对于将来灵活的全光网络应用具有重要的意义。在本文中我们从数值上分析了幅度调制信号,相位调制信号,以及混合幅度调制信号和相位调制信号的多信道波长转换技术。本文同时也讨论了受激布里渊散射效应及其对于基于四波混频效应的高效波长转换技术的影响。分析结果表明差分相位调制信号（DPSK）更加适合基于四波混频效应的多信道波长转换技术,因为多信道OOK波长转换的信号将会受到无法避免的码型相关损耗效应的影响。在将来的应用中,当调制格式由传统的OOK格式部分升级为DPSK格式的时候,在多信道波长转换情况下的OOK信号对于升级的DPSK信号的影响必须要仔细考虑,并且这种影响随着OOK信道数目的增加变得更加严重。因此我们可以得出如下结论,DPSK信号更加适合于传输和多信道波长转换的需要,尤其是在长距离传输和高比特速率的系统中。     

Experimental Demonstrations of All-Optical Phase-Multiplexing Using FWM-Based Phase Interleaving in Silica and Bismuth-Oxide HNLFs

We propose an all-optical phase-interleaving technology based on dual-pump four-wave mixing (FWM) in highly nonlinear fiber (HNLF). The proposed all-optical phase-interleaving technology is applied in an all-optical phase-multiplexing scheme to successfully phase-multiplex 2x or 3$,times,$10-Gb/s DPSK-WDM signals to a 20- or 30-Gb/s DPSK in non-return-to-zero (NRZ) formats. The proposed all-optical phase multiplexing scheme is demonstrated using dual-pump FWM in highly nonlinear silica and bismuth fibers. In contrast with optical time-division multiplexing technology, the proposed all-optical phase-multiplexing technology does not require pulse-carving, thus offering a high spectral-efficiency. Differential precoder for each input tributary is operated independently, and no additional encoder or postcoder is required to recover the original data after demodulation on the receiver side.      

40-Gb/s Time-Division-Multiplexed Passive Optical Networks Using Downstream OOK and Upstream OFDM Modulations

In this investigation, we first propose and investigate a 40-Gb/s time-division-multiplexed passive optical network (TDM-PON) using four wavelength-multiplexed signals in both downstream and upstream traffic. Here, each downstream signal uses 10-Gb/s on–off keying (OOK) format encoded by a Mach–Zehnder modulator (MZM) in 1.5-$mu{hbox {m}}$ band. And each upstream channel utilizes the highly spectral efficient 10-Gb/s orthogonal frequency-division-multiplexing quadrature amplitude modulation (OFDM-QAM) generated by directly modulating a 1.3-$mu{hbox {m}}$ laser. Based on the proposed scheme, 40-Gb/s data traffic in a TDM-PON can be obtained easily by using four wavelength-multiplexed channels. In addition, the performance of the proposed PON architecture has also been discussed.      

High-Resolution Optical Sampling of 640-Gb/s Data Using Four-Wave Mixing in Dispersion-Engineered Highly Nonlinear As$_2$S $_3$ Planar Waveguides

We present the first demonstration of an optical sampling system, using the optical Kerr effect in a chip-scale device, enabling combined capability for femtosecond resolution and broadband signal wavelength tunability. A temporal resolution ${ ≪ }500$ fs is achieved using four-wave mixing in a 7-cm-short chalcogenide planar waveguide. The use of a short length, dispersion-shifted waveguide with ultrahigh nonlinearity ($10^4;{rm W}^{-1}{cdot}{rm{km}}^{-1}$) enables high-resolution optical sampling without the detrimental effect of chromatic dispersion on the temporal distortion of the signal and sampling pulses, as well as their phase mismatch. Using the device, we successfully monitor a 640-Gb/s optical time-division multiplexing (OTDM) datastream, showcasing its potential for integrated chip-based monitoring of signals at bitrates approaching and beyond Tb/s. We discuss fundamental limitations and potential improvements.      

Investigation of Transparency of FWM in SOA to Advanced Modulation Formats Involving Intensity, Phase, and Polarization Multiplexing

We experimentally investigate the real transparency of four-wave mixing (FWM) in semiconductor optical amplifiers to modulation formats involving intensity, phase, and polarization multiplexing. We exploit two different FWM polarization-independent schemes (that make use of two pumps) to wavelength-convert 40 Gb/s single-polarization and 80 Gb/s polarization-multiplexed signals in case of both nonreturn-to-zero ${ON}$ –${OFF}$ keying (NRZ-OOK) and NRZ differential phase-shift keying modulation formats. We found that, although FWM conversion is transparent to modulation formats employing phase and intensity, polarization-multiplexed signals pose serious limitations to all-optical processing transparency.      

640 Gbit/s (64-Wavelength $,times,$10 Gbit/s) Data-Rate Wide-Colored NRZ-DPSK Optical Packet Switching and Buffering Demonstration

We demonstrated optical packet switching and buffering operation of a DWDM/NRZ-DPSK optical packet, whose payload-data-rate is 640 Gbit/s (64-wavelength$,times,$10 Gbit/s), for transparent optical packet switch systems for the first time. Error-free (bit-error-rate ${≪}10^{- 9}$) operation including 200-Gchip/s PSK optical label processing was achieved for all 64-wavelength-channel 10 Gbit/s DPSK packet-payloads. In addition, the higher tolerance of DPSK format for packet power fluctuation compared with OOK one was verified in an optical packet switch system.      

Self-Pumping Wavelength Conversion for DPSK Signals and DQPSK Generation Through Four-Wave Mixing in Highly Nonlinear Optical Fiber

A novel scheme is proposed to achieve self-pumping wavelength conversion for two differential phase-shift keying (DPSK) signals at different wavelengths through four-wave mixing (FWM) effect in a highly nonlinear optical fiber. By changing the phase modulation depths to pi/2 for both of the DPSK signals, the two signals can be multiplexed to generate a differential quadrature phase-shift keying signal. The simulations and experimental results demonstrate the feasibility of phase manipulations for phase-shift keying signals through the FWM process     

Highly efficient multichannel wavelength conversion of DPSK signals

This paper demonstrates a multichannel wavelength conversion of differential phase-shift-keyed (DPSK) signals using four-wave mixing in a highly nonlinear fiber. The wavelengths of three 10-Gb/s nonreturn-to-zero (NRZ) DPSK channels are simultaneously converted without incurring the cross-gain modulation penalty usually associated with on-off-keyed signals. A maximum conversion efficiency of 85% was achieved for both NRZ and return-to-zero DPSK signals.     

All-Optical RZ-DPSK WDM to RZ-DQPSK Phase Multiplexing Using Four-Wave Mixing in Highly Nonlinear Fiber

We propose and experimentally demonstrate an all-optical phase multiplexing scheme using four-wave mixing in a highly nonlinear fiber. Two 10-Gb/s pi/2-shifted return-to-zero (RZ) differential phase-shift-keying (DPSK) wavelength-division-multiplexing (WDM) signals are successfully phase-multiplexed into a 20-Gb/s RZ differential quadrature phase-shift-keying signal with a negative 1.6-dB power penalty. With more input DPSK WDM signals, the proposed scheme can be applied to obtain a multilevel phase-shift-keying signal with increased capacity and enhanced spectral efficiency.     

Impact of Channel Plan and Dispersion Map on Hybrid DWDM Transmission of 42.7-Gb/s DQPSK and 10.7-Gb/s OOK on 50-GHz Grid

We investigate experimentally the performance of 42.7-Gb/s return-to-zero (RZ) differential quadrature phase-shift-keyed (DQPSK) channels in a dense wavelength-division-multiplexed transmission system having 10.7-Gb/s nonreturn-to-zero (NRZ) on-off keyed (OOK) channels. Cross-phase modulation (XPM) from the OOK channels is found to be a dominating nonlinear penalty source for copropagating DQPSK channels in a dispersion-managed transmission link with multiple standard single-mode fiber spans. It is also found that the XPM penalty strongly depends on channel occupancy and residual dispersion per span (RDPS). Large RDPS effectively mitigates XPM even for the worst-case occupancy where a 42.7-Gb/s RZ-DQPSK channel is amidst several 10.7-Gb/s NRZ-OOK channels on a 50-GHz channel grid.     

80-Gb/s Low-Driving-Voltage InP DQPSK Modulator With an n-p-i-n Structure

We present a traveling-wave-electrode InP-based differential quadrature phase-shift keying modulator with a novel n-p-i-n waveguide structure. The structure features low electrical and optical propagation losses, which allow the modulator to operate at a high bit rate together with a low driving voltage and a low insertion loss. We successfully demonstrate 80-Gb/s modulation with a driving voltage of only 3 $hbox{V}_{rm pp}$ in a push–pull configuration. The chip size is just 7.5 mm$, times ,$ 1.3 mm.      

Simultaneous 4 × 10 Gb/s NRZ-to-RZ Modulation Format Conversion in Nonlinear Optical Loop Mirror With a Photonic Crystal Fiber

Orthogonal cross-phase-modulation (XPM) scheme in a nonlinear optical loop mirror (NOLM) is proposed to simultaneously convert four synchronized 10-Gb/s nonreturn-to-zero signals into return-to-zero (RZ) format. Modulation format conversion is achieved by using a synchronized optical control pulse train as the pulse carver in a NOLM. The control pulse train and the targeted signals are orthogonal in their states of polarization. This orthogonal nonlinear interaction substantially suppresses the undesirable four-wave mixing (FWM) induced crosstalk in the multichannel operation. Experimental demonstration of the proposed scheme shows that the suppression of the generated FWM idler is >26 dB. Error-free operation is achieved for the four converted 10-Gb/s RZ signals in a single NOLM by sharing the nonlinear XPM effect induced by the control pulse train.     

A Fully Integrated 0.13- $mu$m CMOS 40-Gb/s Serial Link Transceiver

A fully integrated 40-Gb/s transceiver fabricated in a 0.13-$mu$m CMOS technology is presented. The receiver operates at a 20-GHz clock performing half-rate clock and data recovery. Despite the low ${rm f}_{rm T}$ of 70 GHz, the input sampler achieves 10-mV sensitivity using pulsed latches and inductive-peaking techniques. In order to minimize the feedback latency in the bang-bang controlled CDR loop, the proportional control is directly applied to the VCO, bypassing the charge pump and the loop filter. In addition, the phase detection logic operates at 20 GHz, eliminating the need for the deserializers for the early/late timing signals. The four clock phases for the half-rate CDR are generated by a quadrature LC-VCO with microstrip resonators. A linear equalizer that tunes the resistive loading of an inductively-peaked CML buffer can improve the eye opening by 20% while operating at 39 Gb/s. The prototype transceiver occupies 3.4$, times ,$2.9 mm$^{2}$ with power dissipation of 3.6 W from a 1.45-V supply. With the equalizer on, the transmit jitter of the 39-Gb/s 2$^{15}-1$ PRBS data is 1.85 ${rm ps}_{rm rms}$ over a WB-PBGA package, an 8-mm PCB trace, an on-board 2.4-mm connector, and a 1 m-long 2.4-mm coaxial cable. The recovered divided-by-16 clock jitter is 1.77 ${rm ps}_{rm rms}$ and the measured BER of the transceiver is less than $10^{- 14}$ .      

Optimization of fiber Raman amplifier by reduction of four wave mixing effect

We analyzed the four wave mixing (FWM) effect by propagating two channels through the same backward pumped fiber Raman amplifier (FRA) with variations in FRA parameters. It is observed that FWM increases with increase in signal input power as well as pump power. The FWM effect is also analyzed for Raman constant \(({f}_{\text{ r }})\) to obtain the optimum value of \(({f}_{\text{ r }})\) , and it is found that to have minimum FWM, the optimum value of Raman constant comes out to be 0.18. This Raman amplifier can be used for wavelength division multiplexed application with constant broadband gain.     

All-Optical Modulation-Format Convertor Employing Polarization-Rotation-Type Nonlinear Optical Fiber Loop Mirror

An all-optical modulation-format convertor with regenerative function based on fiber nonlinearity is proposed and demonstrated. The convertor was formed utilizing polarization- rotation-type nonlinear optical fiber loop mirror and could operate at both on–off keying (OOK) to OOK and OOK to phase-shift keying (PSK) format conversions only by simply rotating the optical axis of the intra $lambda/2$ waveplate, without excess-loss generation and realignment of the driving conditions of control optical signals in the format exchange. The 40-Gb/s OOK to OOK/PSK format conversions were successfully performed utilizing this new type of the all-optical convertor. The results also revealed that this convertor has a reshaping function to degraded control signals as an inline all-optical regenerator.      

A 10-Gb/s Inductorless CMOS Analog Equalizer With an Interleaved Active Feedback Topology

A 10-Gb/s low-power analog equalizer for a 10-m coaxial cable has been realized in 0.13- $muhbox{m}$ CMOS technology. To compensate the cable loss of 20 dB at 5 GHz, this equalizer with an interleaved active feedback topology is proposed without using inductors. Moreover, additional capacitive and resistive source degenerations are incorporated to meet low-frequency losses. This circuit consumes only 14 mW (excluding the output buffer) from a 1.2-V supply with the output swing up to 400 $hbox{mV}_{rm pp}$, and it occupies $0.38 times 0.34 hbox{mm}^{2}$. For 8-, 9-, and 10-Gb/s pseudorandom binary sequences (PRBSs) of $2^{31} - 1$, the measured maximum peak-to-peak jitters are 26, 34, and 40 ps, respectively, and the measured bit error rate (BER) is less than $10^{-12}$.      

Wavelength conversion by cavity-enhanced injection-locked four-wavemixing in a fiber-Bragg-grating coupled diode laser

Four-wave mixing (FWM) in a fiber-Bragg-grating (FBG) coupled semiconductor laser is investigated. We show that a large resonance enhancement of the FWM conversion efficiency can be obtained when the laser cavity is injection-locked by the converted signal, and apply this technique to the wavelength conversion of 1-Gb/s modulated signals. Furthermore, we discuss how the spectral width of these resonances can be increased to make this approach suitable to higher bit rates