Multi-wavelength Optical Source Research Articles

Scalable and Fast Optical Circuit Switch Based on Colorless Coherent Detection: Design Principle and Experimental Demonstration

We investigate a large-scale and fast optical circuit switch system that uses digital coherent technologies. The achievable port count is expanded by introducing colorless detection which eliminates channel selecting filters at receivers. Wavelength selection is performed using a shared local oscillator (LO) bank, which is configured by combining a multi-wavelength optical source with Silicon-photonic tunable filters (TFs). Microsecond switching times are realized with the thermo-optic effect available with the Silicon-photonic TF. Design optimization of the proposed system handles complex level of freedom, i.e., available wavelength number, space switch port count, optical amplifier location and gain, and device loss. In addition, colorless coherent detection induces penalties, which further complicates switch scale assessment. In this paper, we develop a simulator to clarify how those parameters affect switch performance; the switch throughput is maximized with consideration of the degradation stemming from colorless detection. The design performance accurately matches results measured in various system scenarios. A dual-carrier 256-Gb/s DP-QPSK experiment successfully demonstrates a 1,856 × 1,856 optical switch system with switching time under 3.52 μs. The resulting total throughput is 441 Tb/s assuming 7%-overhead HD-FEC. To the best of our knowledge, this is the first demonstration of 400-Tbps class large bandwidth optical switches that use TFs as wavelength selective devices for coherent detection.

Long-wave infrared multi-wavelength optical source for standoff detection of chemical warfare agents.

We have designed and built a wavelength-tunable optical source for standoff detection of gaseous chemicals by differential absorption spectrometry in the long-wave infrared. It is based on a nanosecond 2 µm single-frequency optical parametric oscillator, whose idler wave is amplified in large aperture Rb:PPKTP crystals. The signal and idler waves are mixed in ZnGeP2 crystals to produce single-frequency tunable radiation in the 7.5-10.5 µm range. The source was integrated into a direct detection lidar to measure sarin and sulfur mustard inside a closed chamber, in an integrated path configuration with a noncooperative target.

56 Gb/s/λ over 1.3 THz frequency range and 400G DWDM PAM-4 transmission with a single quantum dash mode-locked laser source.

The continued evolution of high capacity data center interconnects (DCI) requires scalable transceiver design. The Gigabit Ethernet (GbE) family of standards targets cost-effective and increased capacity transmission through the use of coarse wavelength division multiplexing (CWDM) and direct detection. Moving beyond near-term GbE deployments, multi-wavelength optical sources will be required to enable spectrally efficient WDM transmission, as well as small form-factor transceiver design. This work highlights the capability of a single section 32.5 GHz quantum-dash mode locked laser to provide >Tb/s capacity by demonstrating successful 50 Gb/s/λ pulse amplitude modulation transmission on modes spanning a >1 THz frequency range. Additionally, true 400G DWDM (8×56 Gb/s) C-band transmission is successfully demonstrated with the Q-Dash MLL, resulting in a spectral efficiency of 1.54 b/s/Hz.

Tunable and flat single-notch microwave photonic filter with multi-wavelength optical source

A tunable and flat single-notch microwave photonic filter (SNMPF) with a multi-wavelength optical source is proposed and demonstrated. In the experiment, the multi-wavelength optical source is based on a tunable laser and a broadband optical source, which has the ability to achieve separate control of the first tap and secondary taps. Through a large number of tap amplitude tests and simulations, the filter can achieve a flat-passband; the passband ripples are smaller than 0.65 dB. The notch depth of the SNMPF is tuned by changing the amplitude of the first tap. The frequency of the SNMPF is continuously tuned by controlling the Fourier-domain optical processor to induce an additional phase, and the 3 dB bandwidth of the filter is tuned by controlling the waveshaper to adjust the number of taps. For simulation results, the depth of the SNMPF is tuned from −43 dB to −14.73 dB, the center frequency is tuned continuously from 0 GHz–74.488 GHz, the bandwidth with 10-taps is 3.54 GHz and the SNMPF has a flat-passband.

Continuously tunable microwave photonic filter with multiwavelength optical source

A continuously tunable microwave photonic filter (MPF) with a multiwavelength optical source is proposed and demonstrated. The proposed MPF is based on a broadband optical source (BOS) and a waveshaper, which serves as a programmable slicing optical filter. By programming the waveshaper, a 50-channel stable and flat optical source is realized experimentally. The amplitude and phase of the optical carriers and phase modulation sidebands are then controlled via a Fourier-domain optical processor (FD-OP); phase modulation is changed to single sideband modulation. This filter could also be switched from bandpass to notch filter by controlling FD-OP. As simulation results, the center frequency of the bandpass filter is tuned continuously from 0 to 37.244 GHz in the entire free spectral range (FSR) and this notch filter based on 50 taps has the ability of realizing a narrow-notch, flat-passband, and large FSR response.

Widely tunable microwave photonic filter based on four-wave mixing

A microwave photonic filter (MPF) based on four-wave mixing (FWM) is proposed and experimentally demonstrated. Two single-frequency laser beams produce the four-wave-mixing effect in a highly nonlinear fiber and generate a multiwavelength optical signal output. The multiwavelength optical signal is used to generate the multitaps of the MPF. The wavelength spacing of the multiwavelength optical source is equal to the frequency difference of the two input laser beams. By changing the frequency difference of the two input laser beams, wavelength spacing of the multiwavelength optical source output can be continuously tuned in the range of 0.36 to 1.6 nm. Thus the center frequency of the filter can be continuously tuned within the range of 6.914 to 30.729 GHz.

Near-infrared spectroscopic photoacoustic microscopy using a multi-color fiber laser source.

We demonstrate a simple multi-wavelength optical source suitable for spectroscopic optical resolution photoacoustic microscopy (OR-PAM) of lipid-rich tissue. 1064 nm laser pulses are converted to multiple wavelengths beyond 1300 nm via nonlinear optical propagation in a birefringent optical fiber. OR-PAM experiments with lipid phantoms clearly show the expected absorption peak near 1210 nm. We believe this simple multi-color technique is a promising cost-effective approach to spectroscopic OR-PAM of lipid-rich tissue.

Eight‐tap transversal filter using a multiwavelength optical source and a dispersive fiber

ABSTRACTWe propose and experimentally demonstrate an eight‐tap transversal filter using a multiwavelength optical source and a dispersive fiber. The multiple wavelengths corresponding to taps are generated by combining broadband optical sources with the arrayed waveguide gratings providing equal wavelength spacing. This method has the advantage of providing a constant time delay between taps together with a dispersive medium (i.e., fiber). The free spectral range (FSR) of the filter is changed by controlling the fiber length. The experimental results showed an FSR of 7.03 GHz and a main to secondary sidelobe ratio of 12.1 dB with 0.8‐nm wavelength spacing, and 3.46 GHz and 13.4 dB with 1.6‐nm wavelength spacing, respectively. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:942–945, 2015

Research of an integrative technique with polarization modulation for generating high-quality multi-wavelength optical source

With the development of society, the need of fiber optical communication expansion and upgrades is increasing. Multi-wavelength optical source has been popularly researched as one of the key component of DWDM. A integrative technique with polarization modulation for high-quality multi-wavelength optical source has been proposed theoretically and experimentally. A comprehensive and systematic overview of how to get a high-quality multi-wavelength optical source, based on in-depth and detailed experiment research. It is found that the optical intensity of the sidebands are not only related to the microwave source and DC bias voltage loaded at EOIM, but also affected by the polarization state of the input light. Five perfect sidebands with equal peak value can be realized by regulating the polarization state of the input light, in addition to regulating the microwave source and DC bias voltage loaded at EOIM as well as. The peak–peak difference of intensity of sidebands can be down to 0.00dBm in the best situation. Polarization state of the input light plays a good role in generating wonderful sidebands with equal space, balanced peak value, high signal-to-noise ratio. The number of sidebands can be selected according to specific application. The findings may have important implications for high-quality multi-wavelength optical source.

Reconfigurable microwave photonic filter with negative coefficient based on an optoelectronic oscillator

We report a reconfigurable multi-tap microwave photonic filter with negative coefficient based on an optoelectronic oscillator (OEO). The key novelty of this work is that a single polarization modulator (PolM) is used to build the OEO as well as to generate a multi-wavelength optical source. Thus, an external microwave source which is usually involved in the generation of multi-wavelength optical source by externally modulating a single tone optical beam is saved. In addition, the spectrum of the multi-wavelength optical source is reconfigurable in terms of the number of the optical components and the frequency interval between the adjacent components. The negative coefficient of the microwave photonic filter is achieved using a phase modulator (PM) and a dispersive element. The proposed approach is theoretically analyzed and experimentally verified. The generated fundamental microwave signal has a frequency of 9.95GHz and a phase noise of −118dBc/Hz at 10kHz offset. By adjusting the optical power inside the OEO loop and the polarization controller (PC) outside the OEO loop, the tap number of the microwave photonic filter can be adjusted from 2 to 5, leading to a reconfigurable microwave photonic filter. The measured frequency responses of the microwave photonic filters agree well with the simulated ones.

A band-pass microwave photonic filter based on Lyot-Sagnac filter and cascaded optical structures

A band-pass microwave photonic filter (MPF) based on Lyot-Sagnac filter and two cascaded optical structures is demonstrated. In the experiment, a stabilized and tunable multi-wavelength optical source is obtained by slicing the broadband optical source (BOS) with a Lyot-Sagnac filter. A standard single-mode fiber (SMF) and a fiber ring resonator are cascaded to improve the mainlobe-to-sidelobe suppression ratio (MSSR) and Q-factor of the filter. The analysis shows that MSSR and Q-factor are improved by reducing the split ratio of the coupler or increasing the length of fiber in fiber ring resonator. The results have significant guidance for MPF design by choosing appropriate devices and parameters. Based on the analyses, a band-pass filter with MSSR of 53.54 dB and Q-factor of 4048 is achieved by choosing the split ratio of 0.01, the length of SMF of 30 km and the length of fiber in fiber ring resonator of 152.27 cm.

A tunable microwave photonic filter with complex coefficient based on slicing spectrum and stimulated Brillouin scattering

In this paper, we propose a method to realize microwave photonic filter (MPF) with complex coefficient, whose central frequency f 0 and 3 dB bandwidth are tunable. The complex coefficient is realized by multi-wavelength optical source and stimulated Brillouin scattering (SBS). The central frequency of the filter is tuned by adjusting the phase shift caused by SBS without changing its frequency response. The frequency selectivity of filter can be improved through increasing the bandwidth of broadband optical source (BOS) or decreasing wavelength separation to increase the taps of MPF. The mainlobeto-sidelobe suppression ratio (MSSR) of the filter is affected by the weight of each tap. When the length of fiber is 0.5544 m in birefringence fiber loop mirror (FLM), the MSSR is improved by 18.55 dB compared with that without the weight controlling.

Simultaneous distributed strain and temperature sensing based on combined Raman–Brillouin scattering using Fabry–Perot lasers

An investigation is performed of the possibility of achieving simultaneous distributed strain and temperature sensing based on hybrid Raman–Brillouin scattering with the use of multi-wavelength optical sources such as common Fabry–Perot (FP) lasers. By employing a self-heterodyne detection scheme based on a multi-wavelength optical local oscillator, the benefits of FP lasers are fully exploited, allowing for high-power Raman intensity measurements and a simultaneous high-accuracy detection of the Brillouin frequency shift parameter for each FP longitudinal mode. Experimental results point out a significant reduction of coherent Rayleigh noise, and highlight the enhanced performance in hybrid Raman–Brillouin sensing when using FP lasers; in particular using standard FP lasers at 1550 nm results in about 12 dB (7 dB) temperature (strain) accuracy improvement at 25 km sensing distance with respect to the use of standard distributed feedback lasers.

Multiwavelength Optical Source for OCDM Using Sinusoidally Modulated Laser Diode

This paper reports a novel cost-effective multiwavelength optical source for OCDM. This source has a simple configuration and emits well-flattened light with a precisely controlled wavelength spacing by using a directly sinusoidally modulated laser diode technique. The flattened multiwavelength light generation is analytically evaluated by using a small signal approximation. The application of the proposed optical source to OCDM was demonstrated experimentally.

Bidirectional 1.25-Gbps Wired/Wireless Optical Transmission Based on Single Sideband Carriers in Fabry–PÉrot Laser Diode by Multimode Injection Locking

A new bidirectional wavelength-division-multiplexed radio-over-fiber system to simultaneously transmit both wired and wireless gigabit data is proposed. A Fabry-Perot laser diode is used as a multiwavelength optical source. Multimode injection locking technique is implemented to create single sideband carriers for several base stations. Reflective semiconductor optical amplifiers are used as modulators for both uplink and downlink. The experimental demonstration showed that bidirectional 1.25-Gbps wired and 15-GHz wireless data transmission with bit error rate (BER) < 10-9 for three channels after 23 km was accomplished. Moreover, mitigation of RF signal distortion due to chromatic-dispersion effect was observed.

A tunable and reconfigurable microwave photonic filter based on two cascaded modulators and a dispersive medium

A novel tunable and reconfigurable microwave photonic filter based on two cascaded modulators and a dispersive medium is proposed, theoretically discussed and experimentally demonstrated. A single-wavelength LD and a modulator (either a Mach–Zehnder modulator or a phase modulator which can avoid the dc bias drift problem) are used to obtain a multi-wavelength optical source. By adjusting the modulation frequency and the bias voltage on the modulators, the wavelength spacing and the relative amplitude of the optical tones change, thus making the filter tunable and reconfigurable. The experimental results show that the proposed filters have good tunability and reconfigurability and the mainlobe-to-sidelobe ratio of around 25 dB is achieved.

A reconfigurable multiwavelength fiber laser with switchable wavelength channels and tunable wavelength spacing

We report the experimental demonstration of a reconfigurable multiwavelength fiber laser source with switchable wavelength channels and tunable wavelength spacing by spectrum slicing a broadband light source using a tunable comb filter. The tunable comb filter is based on a thermally-induced linearly-chirped fiber Bragg grating (LCFBG). As an example to demonstrate the effectiveness of the method, two wavelength channels with various wavelength spacings and eight wavelength channels with ∼1.6 nm wavelength spacing were experimentally demonstrated. All the wavelength channels have rejection ratios of greater than 20 dB, and very small 3-dB linewidths of ∼10 pm. The multiwavelength optical source has such unique advantages as simple all-fiber structure, switchable wavelength channels, tunable wavelength spacing, very narrow linewidths, and stable room-temperature operation.

Optical True Time-Delay for Two-Dimensional $X$-Band Phased Array Antennas

An optical true time-delay (TTD) scheme for two-dimensional (2-D) X-band phased array antennas (PAAs) has been proposed. It is composed of a multiwavelength optical source and a delay line matrix consisting of 2times2 optical microelectromechanical system (MEMS) switches with fiber-optic delay lines connected between cross ports. A 2-bit times 4-bit optical TTD for 10-GHz 2-D PAAs has been implemented by cascading a wavelength-dependent TTD (WD-TTD) with a unit time delay of 12 ps in the x-direction and a wavelength-independent TTD (WI-TTD) with that of 6 ps in the y-direction. The time delay error for WD-TTD was measured to be less than 2.8 ps, mainly due to jitter incurred from gain-switching. On the other hand, the error for WI-TTD was less than 0.8 ps, which is within the equipment resolution. Insertion loss of both delay line matrices was less than 1 dB due to the column-wise control of the MEMS switches. This prevents the feed current applied to each antenna element from fluctuating at any radiation angles so that antenna gain and sidelobe level do not deteriorate in this scheme

Influence of degenerate four-wave mixing on the performance of supercontinuum-based multiwavelength optical source

length optical source has been investigated in detail experimentally and theoretically. Numerical simulation results show that the degenerate FWM effect has a deteriorative influence on the spectral uniformity and the optical signal-to-noise ratio (OSNR) of supercontinuum-based optical source, and by suppressing degenerate FWM effect the performance enhancement of the supercontinuum can be achieved successfully. These results are also confirmed by our experiments. Experimentally, by suppressing degenerate FWM the crosstalk of adjacent channels to the filtered channel can be reduced by as much as 15 dB, and consequently the measured receiver sensitivity at 10 Gbit/s for the filtered optical source is improved from 1.7 to 17.8 dBm.

Multichannel fiber gratings with tailored dispersion profiles for RF filtering

A wide-band continuously tunable microwave photonic filter based on a novel multichannel chirped fiber Bragg grating is demonstrated. The four-tap filter demonstrates continuous tuning from 4.5 to 14 GHz through the use of uniquely incrementing dispersion profiles written within each channel of the grating. This allows for a simplified tuning method based on the collective wavelength tuning of a single multiwavelength optical source over a narrow wavelength range.