All-optical Time-division Demultiplexing Research Articles

An integrated nonlinear optical loop mirror in silicon photonics for all-optical signal processing

The nonlinear optical loop mirror (NOLM) has been studied for several decades and has attracted considerable attention for applications in high data rate optical communications and all-optical signal processing. The majority of NOLM research has focused on silica fiber-based implementations. While various fiber designs have been considered to increase the nonlinearity and manage dispersion, several meters to hundreds of meters of fiber are still required. On the other hand, there is increasing interest in developing photonic integrated circuits for realizing signal processing functions. In this paper, we realize the first-ever passive integrated NOLM in silicon photonics and demonstrate its application for all-optical signal processing. In particular, we show wavelength conversion of 10 Gb/s return-to-zero on-off keying (RZ-OOK) signals over a wavelength range of 30 nm with error-free operation and a power penalty of less than 2.5 dB, we achieve error-free nonreturn to zero (NRZ)-to-RZ modulation format conversion at 10 Gb/s also with a power penalty of less than 2.8 dB, and we obtain error-free all-optical time-division demultiplexing of a 40 Gb/s RZ-OOK data signal into its 10 Gb/s tributary channels with a maximum power penalty of 3.5 dB.

Applications of Highly-Nonlinear Chalcogenide Glass Devices Tailored for High-Speed All-Optical Signal Processing

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Ultrahigh nonlinear tapered fiber and planar rib Chalcogenide waveguides have been developed to enable high-speed all-optical signal processing in compact, low-loss optical devices through the use of four-wave mixing (FWM) and cross-phase modulation (XPM) via the ultra fast Kerr effect. Tapering a commercial <formula formulatype="inline"><tex> $\hbox{As}_{2}\hbox{Se}_{3}$</tex> </formula> fiber is shown to reduce its effective core area and enhance the Kerr nonlinearity thereby enabling XPM wavelength conversion of a 40 Gb/s signal in a shorter 16-cm length device that allows a broader wavelength tuning range due to its smaller net chromatic dispersion. Progress toward photonic chip-scale devices is shown by fabricating <formula formulatype="inline"> <tex>$\hbox{As}_{2}\hbox{S}_{3}$</tex></formula> planar rib waveguides exhibiting nonlinearity up to <formula formulatype="inline"><tex>$2080\, {\rm W}^{-1}\cdot \hbox{km}^{-1}$</tex></formula> and losses as low as 0.05 dB/cm. The material's high refractive index, ensuring more robust confinement of the optical mode, permits a more compact serpentine-shaped rib waveguide of 22.5 cm length on a 7-cm-size chip, which is successfully applied to broadband wavelength conversion of 40–80 Gb/s signals by XPM. A shorter 5-cm length planar waveguide proves most effective for all-optical time-division demultiplexing of a 160 Gb/s signal by FWM and analysis shows its length is near optimum for maximizing FWM in consideration of its dispersion and loss. </para>

Polarization-Insensitive All-Optical Time-Division Demultiplexing Using a Fiber Four-Wave Mixer With a Peak-Holding Optical Phase-Locked Loop

We demonstrate a simple scheme for the all-optical time-division demultiplexer, featuring a polarization-independent optical gate and a peak-holding optical phase-locked loop (PLL) for clock recovery. A fiber four-wave mixer (FWM) is employed as an optical gate. The polarization insensitive operation is achieved by the polarization diversity scheme, where only a short piece of polarization-maintaining fiber is attached to the input port of a conventional fiber FWM. By using the peak-holding optical PLL, the clock pulse is locked to the peak position of the incoming signal pulse. In such a case, a single optical gate acts as the gate switch for time-division demultiplexing as well as the phase detector for phase locking; therefore, the system configuration is greatly simplified. The all-optical time-division demultiplexer we develop enables us to demultiplex a 160-Gb/s signal into 10-Gb/s tributary channels with polarization sensitivity less than 0.5 dB.

All-optical time-division demultiplexing of 160 Gbit/s signal using cascaded second-order nonlinear effect in quasi-phase matched LiNbO 3 waveguide device

Using the cascade of the second-harmonic generation and the difference frequency mixing in a 30 mm-long quasi-phase matched LiNbO3 waveguide device, all-optical time-division demultiplexing of a 160 Gbit/s signal into 10 Gbit/s channels is demonstrated. The power penalty is as small as 2.5 dB at the bit error rate of 10−9, which is attributed to crosstalk of the switch.

All-optical time-division demultiplexing and spatial pulse routing with a GaAs/AlGaAs microring resonator

We report what is to our knowledge the first demonstration of all-optical time-division demultiplexing and spatial pulse routing in a compact nonlinear GaAs/AlGaAs microring resonator operating at 1.55 microm . Switching is through the refractive-index change induced by two-photon absorption. The switching time of the device, limited by the ring-charging time and the recombination time of the induced carriers, is measured to be 30 ps. The switching on-off contrast, limited by the slight mismatch between the input and output coupling coefficients, exceeds 8 dB. The device can be used for time-division multiplexing as well.

All-optical time-division demultiplexing experimentwithsimultaneous output of all constituent channels from 100 Gbit/s OTDM signal

The successful demonstration of all-optical time-division demultiplexing is reported, wherein all 10 Gbit/s constituent channels are simultaneously demultiplexed with no error from a 10 × 10 Gbit/s OTDM signal. A multichannel demultiplexer based on XPM-induced frequency shift in an optical fibre, called MOXIC, is used.

Vibration-insensitive nonlinear optical loop mirror utilizing reflective scheme

We propose a new type of nonlinear optical loop mirror that can reduce nonreciprocal phase shifts due to external vibration. We experimentally confirm its excellent vibration by all-optical time-division demultiplexing of 100-Gb/s optical signal.

Multiple-channel output all-optical OTDMdemultiplexer using XPM-induced chirpcompensation (MOXIC)

The authors present a novel all-optical time-division demultiplexer capable of simultaneously outputting multiple channels at speeds of >100 Gbit/s. Its operation is based on time-wise local chirp compensation of a down-chirped clock pulse through cross-phase modulation (XPM) induced by a signal pulse stream. Error-free, simultaneous six-channel-output, 100 to 6.3 Gbit/s demultiplexing is successfully demonstrated.

Fiber four-wave mixing demultiplexing with inherent parametric amplification

We present an all-optical time-division demultiplexer with 22 dB conversion efficiency, using four-wave mixing (FWM) at 1550 nm in a single-mode dispersion-shifted fiber. Error-free demultiplexing of 20 Gb/s data to 10 Gb/s is obtained, with 1.4 dB power penalty at BER=10/sup -9/. We also derive theoretical expressions for the conversion efficiency, the maximum bit rate that is possible to demur and the shape of the switching window. In particular we emphasize the importance of phase-matching in order to achieve a flat switching window. Furthermore the pump must remain undepleted to avoid a detrimental reduction of the extinction ratio due to instantaneous parametric gain saturation.

Polarisation-independent all-optical demultiplexingup to 200 Gbit/s using four-wave mixingin a semiconductor laser amplifier

Polarisation-independent all-optical time-division demultiplexing is demonstrated up to 200 Gbit/s with &lt;0.5 dB polarisation dependency based on four-wave mixing in depolarised TE and TM modes in a travelling-wave semiconductor laser amplifier.

All-optical time-division demultiplexer using semiconductor switching

An all-optical time-division demultiplexer system is proposed that employs semiconductor switching. The technique can be applied through the use of input infrared signals of wavelengths ≥1 µm. The device is simple to construct and has a potential capacity of 1 Tbit/s, with cross talk between channels of only approximately -13 to -17 dB at operating wavelengths between 1 and 15 µm, respectively. The optimum characteristics and the operational parameters are also presented.

Effects of crosstalk and timing jitter on all-optical time-division demultiplexing using a nonlinear fiber Sagnac interferometer switch

All-optical time-division demultiplexing using a nonlinear fiber Sagnac interferometer switch (NSIS) is studied with respect to the two main causes that degrade the bit-error-rate (BER) performance: crosstalk and timing jitter. It is shown that unwanted cross-phase-modulation in the reference signal which counter-propagates to the control pulse, as well as the poor extinction of the switch itself, seriously degrades the extinction ratio of the switch, thus increasing the crosstalk from other channels. Numerical calculations clarify the effect of the switching window width, window shape, and the multiplexed channel number on the power penalty in terms of BER performance. Timing jitter between the signal and control pulses is investigated as another degradation factor that causes an error floor in BER performance. It is found that the minimum BER is obtained when the window width is set to the time slot width and the rms value of the jitter must be less than 1/14.1 times the time slot width to ensure that BER >

Nonlinear Sagnac interferometer switch and its applications

Ultrafast all-optical switching based on the optical Kerr effect in a Sagnac interferometer which consists of a dichroic polarization-maintaining fiber coupler and dispersion-shifted polarization-maintaining fiber loop is reported. This nonlinear Sagnac interferometer switch has the advantage of high stability originating from completely balanced interfering arms. In addition, because dispersion-shifted fibers were used, increases in switching power and switching time were prevented. Moreover, polarization fluctuation was completely suppressed due to the all-polarization maintaining fiber configuration. The required switching power for complete switching was measured to be 1.8 W for a 200-m-long fiber. All-optical time division demultiplexing and logic operations, including inversion and operation, using the nonlinear Sagnac interferometer switch were successfully demonstrated at 5 Gb/s.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>