Nonlinearly strain-chirped fiber Bragg grating with an adjustabledispersion slope

In this letter, we demonstrate an adjustable dispersion slope compensator for waveform distortion compensation based on a nonlinearly strain-chirped fiber Bragg grating. The dispersion slope of the device can be tuned up to -18.9 ps/nm² with a bandwidth >2.4 nm. After transmission through a 120-km-long dispersion-shifted fiber, the resulting waveform distortion for a 2.65-ps pulse is successfully compensated by using this device     

Performance analysis of a dispersion compensator usingarrayed-waveguide gratings

We have developed a dispersion compensator that uses arrayed-waveguide gratings (AWGs) and a spatial filter. The compensator using AWGs with 380 waveguides in each array and the diffraction order of 53, can compensate a total second-order dispersion of 260 ps/nm with an eye-closure penalty of 1 dB for a 40-Gb/s nonreturn-to-zero (NRZ) signal. It is shown that the required spatial resolution of the spatial phase filter for compensation is 2.55 μm for silica AWGs of usual design. The acceptable fluctuation in the refractive index of the waveguides in the AWGs is as large as 5×10^-5     

Tunable dispersion equalizer with a divided thin-film heater for40-Gb/s RZ transmissions

We have developed tunable dispersion equalizers with a chirped fiber grating on the divided thin-film heater. The divided thin-film heater took an important role in the control of dispersion and dispersion slope. We successfully demonstrated the dispersion control from -304 to -196 ps/nm, the dispersion slope control from +100 to -300 ps/nm², and good performance in 40-Gb/s return-to-zero transmission by using this tunable dispersion equalizer     

Applications of active arrayed-waveguide gratings in dynamic WDMnetworking and routing

We describe how active arrayed-waveguide gratings (AWGs) may find a diverse range of applications in future dynamic wavelength division multiplexed (WDM) networking and routing. Our initial simulations indicate that these applications include dynamic signal power and erbium-doped fiber amplifier (EDFA) gain equalization with a dynamic range of 12 dB, and interchannel amplified spontaneous emission (ASE) suppression by more than 20 dB; optical add/drop multiplexing with passband-flattened channels and suppressions of 15 dB; and dynamic dispersion compensation of up to ±300 ps/nm     

Dispersion slope equaliser using bend-induced positive dispersionslope in coiled pure-silica fibre

The dispersion slope of a dispersion-shifted fibre has been successfully equalised by using a bend-induced positive dispersion slope in a singlemode fibre. We realised the bent fibre dispersion slope equaliser by using a 1.3 μm zero-dispersion pure silica core fibre (PSM). This equaliser provides a dispersion slope of -12.54 ps/nm² /km in the 1.5 μm region     

Tunable Optical Dispersion Compensator Consisting of Simple Optics With Arrayed Waveguide Grating and Flat Mirror

We propose a tunable optical dispersion compensator (TODC) that uses an arrayed waveguide grating (AWG) and a flat mirror. The TODC employs simple and cost-effective optics, and its chromatic dispersion can be changed simply by translating the AWG. We obtained a 3-dB bandwidth of 39 GHz when the dispersion was tuned within 800 ps/nm, and a maximum dispersion of ${pm}$3000 ps/nm.      

Athermal all-polymer arrayed-waveguide grating multiplexer

An athermal arrayed-waveguide grating (AWG) multiplexer relying on an all-polymer approach is reported. The all-polymer AWG consisting of polymer waveguides fabricated on a polymer substrate exhibits excellent performance. By properly adjusting the coefficient of thermal expansion of the polymer substrate, athermal and polarisation-independent AWG devices featuring a wavelength shift of less than ±0.05 nm in the 25-65°C temperature range could be demonstrated     

Colorless tunable optical dispersion compensator based on a silica arrayed-waveguide grating and a polymer thermooptic lens

We present a colorless tunable optical dispersion compensator (TODC) comprised of a silica arrayed-waveguide grating (AWG) directly coupled to a polymer thermooptic lens. Using silica for the AWG allows it to be low loss and manufactured by a standard process, and using polymer for the thermooptic lens allows it to have a large tuning range and low electrical power consumption. This hybrid TODC is fully solid-state and scales to a large figure-of-merit (dispersion range times bandwidth squared). We demonstrate a version with 100-GHz free-spectral range and 1300-ps/nm tuning range with a 3-dB bandwidth >39 GHz and a lens power consumption <74 mW.     

Dynamic dispersion compensation in a 10-Gb/s optical system using anovel voltage tuned nonlinearly chirped fiber Bragg grating

We experimentally demonstrate dynamic dispersion compensation using a novel nonlinearly chirped fiber Bragg grating in a 10-Gb/s system. A single piezoelectric transducer continuously tunes the induced dispersion from 300 to 1000 ps/nm. The system achieves a bit-error rate=10^-9 after both 50 and 104 km of single-mode fiber by dynamically tuning the dispersion of the grating between 500 and 1000 ps/nm, respectively. The power penalty after 104 km is reduced from 3.5 to <1 dB     

The realization of all-pass filters for third-order dispersioncompensation in ultrafast optical fiber transmission systems

Thin film (TF)-based coupled cavity all-pass filters (CCAP) have the potential for providing compact, low-loss, and highly stable third-order dispersion (TOD) compensation in ultrafast optical fiber transmission systems employing optical time-division multiplexing (OTDM). In this paper, a methodology for designing CCAP filters for TOD compensation is presented, First, we develop a theory necessary for designing the cavity structure, that is, mirror reflectivity and cavity spacing, of CCAP filters. As a next step, we discuss how we can represent such filters as TF devices and demonstrate several TF-layer design examples. Finally, a coupled two-cavity filter is constructed and tested. The filter has a center wavelength that can be varied over a range of 8 nm and can compensate for fiber TOD between 2.0 and 15.5 ps ³ over a bandwidth between 3.6 and 1.2 nm, respectively. The peak spectral ripple of the filter is 1.0 dB, The experimentally measured dispersion curves of the filter agree well with the theory     

Grating compensation of third-order fiber dispersion

Subpicosecond optical pulses propagating in single-mode fibers are severely distorted by third-order dispersion even at the fiber's zero-dispersion wavelength (λ₀). Using cross-correlation techniques, the authors measured the broadening of a 100-fs pulse to more than 5 ps after passing through 400 m of fiber near λ₀. The measured asymmetric and oscillatory pulse shape is in agreement with calculations. A grating and telescope apparatus was configured to simultaneously equalize both third- and second-order dispersion for wavelengths slightly longer than λ ₀. Nearly complete compensation has been demonstrated for fiber lengths of 400 m and 3 km of dispersion-shifted fiber at wavelengths of 1560-1580 nm. For the longer fibers, fourth-order dispersion due to the grating becomes important     

Large purely refractive nonlinear index of single crystal P-toluenesulphonate (PTS) at 1600 nm

Z-scan measurements at 1600 nm on single-crystal PTS (p-toluene sulfonate) with single, 65 ps pulses gave a complex nonlinear refractive index coefficient of n₂=2.2(±0.3)×10^-12 cm²/W at 1 GW/cm² and α₂<0.5 cm/GW. This is the first highly nonlinear, organic material to satisfy the conditions imposed by the figures of merit     

Polarisation-insensitive arrayed-waveguide grating multiplexer withSiO2-on-SiO2 structure

An arrayed-waveguide grating multiplexer with SiO₂-on-SiO₂ structure is fabricated in order to achieve polarisation insensitivity. A negligible wavelength response dependence on polarisation of 0.01 nm, which corresponds to a birefringence of-9×10^-6, is realised in a 16 channel arrayed-waveguide grating multiplexer with a wavelength spacing of 0.8 nm     

Performance Analysis of Steepest Descent-Based Feedback Control of Tunable-Dispersion Compensator for Adaptive Dispersion Compensation in All-Optical Dynamic-Routing Networks

In this paper, we report the performance-analysis results of our proposed high-speed and low-cost feedback-control method of a tunable-dispersion compensator (TDC) for adaptive dispersion compensation in all-optical dynamic-routing networks. In this method, we monitor the received waveform in the time domain and control a TDC repeatedly to reshape the waveform by means of the steepest descent method. Transmission experiments and simulations show that the proposed method can compensate for the dispersion quickly over a wide dispersion range. The compensation range is from $-$6000 to 6000 ps/nm in 10-Gb/s transmission. The compensation time is 1–2 s for dispersions within 1000 ps/nm. This method is applicable to the adaptive dispersion compensation in all-optical dynamic-routing networks.      

Compensation for Second-Order Temperature Dependence in Athermal Arrayed-Waveguide Grating Realizing Wide Temperature Range Operation

We propose a new compensation technique for the second-order temperature dependence in a silica-based arrayed-waveguide grating (AWG) multi/demultiplexer with a resin-filled groove that realizes a wide operating temperature range. We newly employ an additional interferometer in the input port and control the optical field perturbation by using a first-mode lightwave at the entrance to the first slab waveguide. We employ the design to fabricate a 32-channel 100-GHz-spacing athermal AWG that is as compact as a conventional AWG, and demonstrate a reduction in the passband wavelength variation from 70 to 22 pm over an extended $-$ 40 $^{circ}hbox{C}$ to 80 $^{circ}hbox{C}$ temperature range.      

A tunable dispersion compensating MEMS all-pass filter

A tunable dispersion compensating filter based on a multistage optical all-pass filter with a microelectromechanical (MEM) actuated variable reflector and a thermally tuned cavity is described. A two-stage device was demonstrated with a tuning range of ±100 ps/nm, 50-GHz passband and a group delay ripple less than ±3 ps. The device has negligible polarization dependence and is suitable for single or multiple channel compensation. An off-axis, two-fiber package with an excess loss <2 dB/stage avoids the need for a circulator. By cascading four stages, a passband to channel spacing ratio of 0.8 is obtained that allows both 40 Gb/s nonreturn-to-zero (NRZ) and return-to-zero (RZ) signals to be compensated     

Stretched fibre based dispersion compensating module for ultra high-speed telecommunication systems

In this work, the potential efficiency of a low-loss, tunable second- and third-order dispersion compensating module based on a stretched optical fibre for ultra high-speed telecommunication systems is analysed. Experimental results at a repetition rate of 640 GHz show that precise dispersion compensation could be achieved in the range of ±0.038 ps/nm by means of an 11.3 cm maximum stretching of a 48 m long dispersion compensating fibre.     

Power penalty for optical signals due to dispersion slope in WDMfilter cascades

We calculate the receiver power penalty due to the accumulated dispersion slope of optical filter cascades in wavelength-division-multiplexed optical networks. For flat-top fiber Bragg grating and thin-film filters, dispersive rather than amplitude filter effects dominate the cascade power penalty, which increases with dispersion slope and signal frequency detuning from the cascade zero-dispersion point. The dispersion slope of these filters varies as the inverse cube of their bandwidth, using increased penalties for narrow filters in systems with small channel spacing, For a 60-GHz-wide Bragg grating filter with a 1.3-ns/nm² dispersion slope, a cascade of 26 filters can be tolerated at 10 Gbit/s with ±5 GHz allowed detuning. Optically preamplified receivers have significantly larger dispersion penalties than thermal-noise-limited receivers     

Estimation of waveguide phase error in silica-based waveguides

A new estimation method is proposed in order to clarify waveguide phase error factors. Using the proposed method, it is possible to analyze such factors as core size error and refractive index error, which cause optical phase error in waveguides. This method is applied to silica-based waveguides to estimate the waveguide phase error. This revealed an average core size error of 2.1×10^-3 μm and an average refractive index error of 1.9×10^-6. Finally, based on the measured phase error values, the optimum arrayed-waveguide grating (AWG) configuration is considered with a view to achieving low crosstalk