Multi-channel Dispersion Compensation Research Articles

On-Chip Multichannel Dispersion Compensation and Wavelength Division MUX/DeMUX Using Chirped-Multimode-Grating-Assisted Counter-Directional Coupler

On-chip optical dispersion compensation and wavelength division multiplexing/demultiplexing (WDM) are highly demanded functions for optical communications. In this work, we proposed a multichannel dispersion compensation structure based on chirped multimode grating within a counter-directional coupler (CMG-CDC). Simultaneous wavelength division multiplexing and demultiplexing can be realized within a compact footprint. A device design for four-channel CMG-CDC at the C/L (1530–1565 nm) band is presented with a channel spacing of 20 nm assisted by a grooved multimode waveguide structure. The average dispersion for all channels is about −2.25 ps/nm with a channel bandwidth of about 3.1 nm. The device is highly compact and highly scalable, which makes it rather convenient for increasing the group velocity dispersion (GVD) and channel number, indicating flexible applications for versatile systems, including typically coarse wavelength division multiplexer four-lane (CWDM4) transceivers.

Integrated-optic chromatic dispersion compensator with completely passive operation and wide operational bandwidth

I report on a fiber chromatic dispersion compensator comprising an array of 100 fixed delay lines sandwiched by a pair of arrayed-waveguide grating-type wavelength filters. The requisite delay for the dispersion compensation is allocated to each demultiplexed wavelength component after the first wavelength filter, and the wavelength components are again multiplexed at the second filter. The flexible capability of delay pattern arrangement enables us to realize various fixed dispersion compensation characteristics. I show transmittance and relative delay time characteristics of a multichannel dispersion compensator for short-distance wavelength division multiplexing communication, and its application to dispersion compensation for a pulse amplitude modulation four signal. I also demonstrate the realization of a dispersion slope compensator for a dispersion-shifted fiber with this configuration.

4 × 25-Gb/s NRZ-OOK Signals Transmission Over a 160-km Single-Mode Fiber Using 10G-Class DML and Photodiode

In this paper, we have experimentally demonstrated the C-band 4 × 25-Gb/s non-return-to-zero on - off -keying (NRZ-OOK) signals over a 160-km single-mode fiber transmission based on 10G-class directly-modulated lasers and photodiodes. The excessive negative dispersion at the receiver side is used to equalize the frequency response of bandwidth-limited directly-modulated signal, therefore enables 25-Gb/s NRZ-OOK transmission based on 10G-class optical devices. By employing a multichannel chromatic dispersion compensation module in the receiver, a single optical device can be used to equalize the frequency response of multiple channels realizing low-cost and high-capacity signal transmission. The results shown in this paper reveal that our proposed scheme would be a promising candidate for a low-cost transition to 100 Gb/s (4 × 25 Gb/s) for the point-to-point metro network applications.

Programmable eye-opener lattice filter for multi-channel dispersion compensation using an integrated compact low-loss silicon nitride platform.

A tunable eye-opening lattice filter for dispersion compensation is demonstrated on an ultra low-loss waveguide platform based on a compact high-aspect ratio Si3N4 core. A programmable 10th order lattice filter is demonstrated by cascading a total of 21 Mach-Zehnder interferometers with programmable delay lines of lengths designed at the baseband data rate. The filter has a footprint of 2.23 cm2 with continuously tunable dispersion from -500 ps/nm to 500 ps/nm. The filter shows a periodic transfer function with a measured FSR of 100 GHz capable of compensating multiple WDM channels with a single device.

Multichannel optical filters with an ultranarrow bandwidth based on sampled Brillouin dynamic gratings

We first propose a multichannel optical filter with an ultra-narrow 3-dB bandwidth based on sampled Brillouin dynamic gratings (SBDGs). The multichannel optical filter is generated when an optical pulse interfaces with an optical pulse train based on an ordinary stimulated Brillouin scattering (SBS) process in a birefringent optical fiber. Multichannel optical filter based on SBDG is generated with a 3-dB bandwidth from 12.5 MHz to 1 GHz. In addition, a linearly chirped SBDG is proposed to generate multichannel dispersion compensator with a 3-dB bandwidth of 300 MHz and an extremely high dispersion value of 432 ns/nm. The proposed multichannel optical filters have important potential applications in the optical filtering, multichannel dispersion compensation and optical signal processing.

Generation of Time- and Wavelength-Interleaved Optical Pulse-Train With Tunable Pulsewidth Based on Dispersion and Sectional Compression

We show analytically as well as experimentally a technique to generate a time- and wavelength interleaved optical pulse-train (TWIPT) with tunable pulsewidth. The technique involves dispersing an initial pulse-train using a standard single-mode-fiber (SMF) followed by sectional dispersion compensation using a tunable multi-channel dispersion compensation module. Using an initial pulse-train with a fixed repetition frequency frep and a tunable multi-channel dispersion compensation module with a fixed frequency spacing between the adjacent channels, our scheme shows that by choosing appropriate value for the length of the SMF, we can generate a N×frep TWIPT in the case when there are N channels within the bandwidth of the initial pulses. By tuning the channel dispersion to be the opposite of the dispersion introduced by the SMF, one is able to generate transform-limited pulsewidths for the TWIPT. Furthermore, tuning the channel dispersion to other values permits pulsewidth tunability. Based on the proposed scheme, using a 2 GHz supercontinuum source as an initial pulse-train, we demonstrate the generation of a 10 × 2 GHz TWIPT with pulsewidth tunability.

S+C+L波段色散斜率补偿光子准晶体光纤

针对光纤通信中的色散补偿,尤其是密集波分复用系统的多信道同时补偿的需求,提出了一种用于宽带色散斜率补偿的光子准晶体光纤.该光纤结构包层空气孔为准晶体排列,并且在纤芯引入了中心缺陷.通过对光纤特性的数值分析表明,在1 460-1 625 nm的光通信波段,该结构光纤的相对色散斜率为0.004 4-0.002 9 nm^-1,相对色散斜率与标准单模光纤近似相等,且负色散值达-2 476 ps·nm^-1·km^-1.对标准单模光纤进行色散补偿后,在S＋C＋L波段色散值为（-0.5-0）ps·nm^-1·km^-1.该光纤可用于对当前光纤通信系统进行宽带色散补偿,实现多信道同时补偿,简化结构,并降低补偿成本.

50-Wavelength Channel-by-Channel Tunable Optical Dispersion Compensator Using a Combination of AWG and Bulk Grating

We propose a novel optical configuration for a multichannel tunable optical dispersion compensator (TODC) with channel-by-channel operation across the entire L-band. The TODC consists of a cyclic frequency arrayed-waveguide grating whose free spectral range coincides with the channel spacing, a bulk grating, and a liquid crystal on silicon. We achieved channel-by-channel compensation over 50 channels with a maximum chromatic dispersion of ±800 ps/nm.

Demonstration of channelized tunable optical dispersion compensator based on arrayed-waveguide grating and liquid crystal on silicon

We propose and demonstrate a multi-channel tunable optical dispersion compensator (TODC) that consists of an arrayed-waveguide grating (AWG) and liquid crystal on silicon (LCOS). By utilizing the AWG with a large angular dispersion and the LCOS with a flexible phase setting, we can construct a compact and flexible TODC that has a wide tuning range of chromatic dispersion. We confirmed experimentally that the TODC could realize channel-by-channel CD compensation for six WDM channels with a ± 800 ps/nm range and a 3 dB bandwidth of 24 GHz. We believe that the multi-channel operation of this TODC will help to reduce the cost and power consumption of high-speed optical transmission systems.

Flexible Chromatic Dispersion Compensation Over Entire $L$-Band for Over 40-Gb/s WDM Transparent Networks Using Multichannel Tunable Optical Dispersion Compensator

We describe the proof-of-concept demonstration of flexible chromatic dispersion compensation over the entire <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> -band region wavelength-division-multiplexing transparent networks operating at over 40 Gb/s using span-by-span compensation with an arrayed-waveguide grating and an liquid crystal on silicon-based multichannel tunable dispersion compensator.

Dispersion Compensation Configuration Applying a Combination of EDC and Tunable-ODC for Extended $L$-Band WDM Transmission

We propose effective polarization-mode dispersion (PMD) and chromatic dispersion (CD) compensation configuration for practical use in the field, taking into consideration the system cost and the field condition such as the CD changes due to fiber temperature dependence or transmission route change, and rapidly fluctuate state of polarization of the signal lightwave. Our configuration combines electric dispersion compensators (EDCs) with fixed taps in each channel with a multichannel tunable optical dispersion compensator (T-ODC) that can simultaneously compensate all channels' accumulated CD. We demonstrate widely extended <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> -band 43-Gb/s-based wavelength-division-multiplexing transmission over 450 km using our dispersion compensation configuration, and obtain effectiveness that the PMD penalty is suppressed by 2 dB at a differential group delay of 33 ps by using the EDC and that the CD penalty is improved by about 2 dB at the accumulated CD change of +/- 30 ps/nm by using T-ODC and EDC.

On the application of PSO algorithm for multichannel polarisation-mode dispersion compensation systems

Particle swarm optimisation (PSO) algorithm is used in multichannel polarisation-mode dispersion (PMD) compensation systems. As an example, the performances of the two-channel system are simulated. The worse channel is compensated and the performances of the other channel are also improved by using only one compensator. The effect of PMD compensation system is obvious and the searching ability of PSO algorithm is strong. These results shows PSO algorithm is a good choice when it is used in multichannel PMD compensation systems.

Multi-channel Bragg gratings based on nonuniform amplitude-only sampling

A novel technique to implement a Bragg grating with multi-channel and high channel-count response based on nonuniform amplitude-only sampling is proposed. Thanks to the nonuniform sampling, a sophisticated phase modulation for the generation of multi-channel spectral response can be equivalently achieved, while the pitch of the Bragg grating is maintained uniform. The principle is presented. Two design examples with two Bragg gratings for multi-channel filtering and for multi-channel chromatic dispersion compensation are provided.

Interleaved sampled Bragg gratings with concatenated spectrum

We design and demonstrate interleaved sampled Bragg gratings with concatenated spectrum which produce high channel counts with simple design and fabrication. These gratings can be applied in multichannel filtering, dispersion compensation, and many other functions. The devices were implemented as reduction-photolithographically written anti-symmetric Bragg gratings

Wideband multichannel dispersion compensation based on a strongly chirped sampled Bragg grating and phase shifts

A novel multichannel dispersion compensator based on a strongly chirped sampled Bragg grating with phase shifts is demonstrated experimentally. With a single phase mask, various channel spacings and dispersion can be achieved by proper control of the sampling period and the phase shifts. A 100 GHz channel-spacing compensator with a dispersion of -1000 ps/nm and another 200 GHz channel-spacing compensator with a dispersion of -500 ps/nm are designed. As an example, a 40 channel, 100 GHz channel-spacing compensator with a dispersion of approximately -560 ps/nm is fabricated. All the designs are based on one phase mask, thus showing the flexibility of our method.

1.6-Tb/s (40/spl times/40 Gb/s) transmission over 44,...,94 km of SSMF with adaptive chromatic dispersion compensation

Full-band 1.6-Tb/s adaptive chromatic dispersion compensation is demonstrated for the first time. A multichannel tunable dispersion compensator is automatically controlled by arrival time detection on one out of 40 wavelength-division-multiplexed transmitted channels.

Using sampled nonlinearly chirped fiber Bragg gratings to achieve 40-Gbit/s tunable multi-channel dispersion compensation

We demonstrate tunable chromatic dispersion in a 4×40-Gbit/s wavelength-division-multiplexed (WDM) transmission experiments using single sampled nonlinearly chirped fiber Bragg grating (NC-FBG) with negligible errors from higher order dispersion or two cascaded inverse sampled NC-FBG to cancel the higher order dispersion within the data’s bandwidth. In both the single FBG and cascaded FBG configurations, <3 dB penalty is achieved for all four WDM channels even though the eye is completely closed without compensation.

Novel multichannel tunable chromatic dispersion compensator based on MEMS and diffraction grating

Using microelectromechanical systems and diffraction grating technologies, a novel tunable chromatic dispersion compensator for multichannel wavelength-division-multiplexing signals was developed. Independent channel-by-channel dispersion tuning with flat top loss spectra was experimentally confirmed.

Phase response design of a polarization-maintaining fiber loop mirror for dispersion compensation

We propose a simple dispersion-compensation filter using a polarization-maintaining fiber loop mirror. Due to the fact that the proposed filter is spectrally periodic and has a relatively large dispersion, it can be used as a multichannel dispersion compensator. The measured delay characteristic agrees with the theory. The delay characteristic can be tuned by changing the power-coupling coefficient of the variable coupler in the loop mirror.

Tunable dispersion compensation at 40-Gb/s using a multicavity etalon all-pass filter with NRZ, RZ, and CS-RZ modulation

We present a multichannel tunable dispersion compensator (TDC) based on multicavity all-pass etalons that is capable of operation at 40 Gb/s. The device has a tuning range of +200/-220 ps/nm with a group delay ripple < /spl plusmn/5 ps over a channel bandwidth of 80 GHz, an overall loss of < 5.2 dB, very low insertion loss ripple, and can operate on any channel on a 200-GHz grid over the C-band. In addition, we present system performance results at 40 Gb/s using NRZ, RZ, and CS-RZ modulation, compensating up to 45 km of nonzero dispersion shifted fiber (NZDSF). Our results show that this device introduces very little excess system penalty with signal frequency drifts of up to 20 GHz when operated near the center of its tuning range. For single channel experiments with fiber, the system penalty increase versus signal detuning is more significant, but can be reduced by dynamically optimizing the device dispersion during detuning. Finally, we demonstrate simultaneous compensation of 4 channels across the C-band over 25 km of NZDSF.