Showing papers in "IEEE Photonics Technology Letters in 2012"
TL;DR: Theoretical results and numerical simulations conclude that the EVM is an appropriate metric for optical channels limited by additive white Gaussian noise.
Abstract: We examine the relation between optical signal-to-noise ratio (OSNR), error vector magnitude (EVM), and bit-error ratio (BER). Theoretical results and numerical simulations are compared to measured values of OSNR, EVM, and BER. We conclude that the EVM is an appropriate metric for optical channels limited by additive white Gaussian noise. Results are supported by experiments with six modulation formats at symbol rates of 20 and 25 GBd generated by a software-defined transmitter.
539 citations
TL;DR: In this paper, the authors presented the first optical modulation at 50 Gb/s with a 3.1dB extinction ratio obtained from carrier depletion based phase shifter incorporated in a Mach-Zehnder interferometer.
Abstract: Optical modulators formed in silicon are the keystone to many low cost optical applications. Increasing the data rate of the modulator benefits the efficiency of channel usage and decreases power consumption per bit of data. Silicon-based modulators which operate via carrier depletion have to the present been demonstrated at data rates up to 40 Gb/s; however, here we present for the first time optical modulation at 50 Gb/s with a 3.1-dB extinction ratio obtained from carrier depletion based phase shifter incorporated in a Mach-Zehnder interferometer. A corresponding optical insertion loss of approximately 7.4 dB is measured.
413 citations
TL;DR: A new wavelet shrinkage approach allows the distributed vibration measurement of 20-Hz and 8-kHz events to be detected over 1-km sensing length with a 5-ns optical pulse, which is equivalent to 50-cm spatial resolution using the single-mode sensing fiber.
Abstract: This letter proposed and demonstrated a wavelet technique to reduce the time domain noise to get submeter spatial resolution in the distributed vibration sensor based on phase optical time domain reflectometry. A new wavelet shrinkage approach allows the distributed vibration measurement of 20-Hz and 8-kHz events to be detected over 1-km sensing length with a 5-ns optical pulse, which is equivalent to 50-cm spatial resolution using the single-mode sensing fiber.
250 citations
TL;DR: In this paper, the first accelerometer based on a polymer optical fiber Bragg grating (FBG) for operation at both 850 and 1550 nm has been presented, which has a flat frequency response over a 1-kHz bandwidth and a resonance frequency of about 3 kHz.
Abstract: We report on the fabrication and characterization of the first accelerometer based on a polymer optical fiber Bragg grating (FBG) for operation at both 850 and 1550 nm. The devices have a flat frequency response over a 1-kHz bandwidth and a resonance frequency of about 3 kHz. The response is linear up to at least 15 g and sensitivities as high as 19 pm/g (shift in resonance wavelength per unit acceleration) have been demonstrated. Given that 15 g corresponds to a strain of less than 0.02% and that polymer fibers have an elastic limit of more than 1%, the polymer FBG accelerometer can measure very strong accelerations. We compare with corresponding silica FBG accelerometers and demonstrate that using polymer FBGs improves the sensitivity by more than a factor of four and increases the figure of merit, defined as the sensitivity times the resonance frequency squared.
163 citations
TL;DR: In this paper, a heterogeneously integrated InP/silicon-on-insulator (SOI) laser source realized through divinylsiloxane-bis-benzocyclobutene (DVS-BCB) wafer bonding is presented.
Abstract: We report on a heterogeneously integrated InP/silicon-on-insulator (SOI) laser source realized through divinylsiloxane-bis-benzocyclobutene (DVS-BCB) wafer bonding. The hybrid lasers present several new features. The III-V waveguide has a width of only 1.7 μm, reducing the power consumption of the device. The silicon waveguide thickness is 400 nm, compatible with high-performance modulator designs and allowing efficient coupling to a standard 220-nm high index contrast silicon waveguide layer. In order to make the mode coupling efficient, both the III-V waveguide and silicon waveguide are tapered, with a tip width for the III-V waveguide of around 800 nm. These new features lead to good laser performance: a lasing threshold as low as 30 mA and an output power of more than 4 mW at room temperature in continuous-wave operation regime. Continuous wave lasing up to 70°C is obtained.
153 citations
TL;DR: In this article, a single pixel plasmonic complementary metal oxide semiconductor (CMOS) photo sensor consisting of a color filter integrated on a CMOS photodiode was fabricated using electron beam lithography and dry etch.
Abstract: A single-pixel plasmonic complementary metal oxide semiconductor (CMOS) photo sensor consisting of a plasmonic color filter integrated on a CMOS photodiode was fabricated using electron beam lithography and dry etch. The photocurrent measurement results confirmed the three primary color filtering responses that could be achieved in a single layer of nanostructured aluminium film. Finite-difference time-domain simulation demonstrated a good agreement of the reflection spectra with the measured result. This research can lead to the development of advanced CMOS image sensors with low cost and low crosstalk.
141 citations
TL;DR: In this paper, a 1.1-Gb/s visible light communication (VLC) system employing carrierless amplitude and phase modulation (CAP) and a commercially available phosphorescent white light emitting diode (LED) was demonstrated.
Abstract: We demonstrate 1.1-Gb/s visible light communication (VLC) employing carrier-less amplitude and phase modulation (CAP) and a commercially available phosphorescent white light emitting diode (LED). Optical blue filtering, precompensation, and decision feedback equalization are used to compensate the frequency response of the phosphor-based white LED. Various modulation orders of CAP signals are investigated to maximize the capacity of the VLC system. The record data rate of 1.1 Gb/s with the bit error rate performance below the FEC limit of 10-3 is successfully achieved >; 23-cm air-transmission via a 220-MBaud 32-CAP signal.
134 citations
TL;DR: In this article, a passive integrated optical circuit for mode-multiplexing and demultiplexing six channels, LP01 and LP11 modes in a few-moded fiber, is designed and tested.
Abstract: A novel passive integrated optical circuit for mode-multiplexing and demultiplexing six channels, LP01 and LP11 modes in a few-moded fiber, is designed and tested. A push-pull solution is proposed and demonstrated to excite the LP11 modes with a high extinction ratio. The circuit can outperform present bulk-optics solutions through its compactness and stability, and it has the potential advantages of high coupling efficiency and excellent mode crosstalk suppression.
132 citations
TL;DR: In this article, a nonadiabatic microfiber sensor with a taper diameter of few micrometers is demonstrated, where the modal interference caused by the abrupt taper results in a sinusoidal spectral response.
Abstract: We demonstrate a nonadiabatic microfiber sensor with a taper diameter of few micrometers. The modal interference caused by the abrupt taper results in a sinusoidal spectral response. The wavelength shift arising because of the changes in the external refractive index is found to be significant, achieving a maximum sensitivity of 18681.82 nm/RIU. The measured results show good agreement with the theoretical predictions. The high sensitivity and the simplicity offer the sensor the potential for many real applications.
130 citations
TL;DR: In this paper, the advantages of spatial superchannels for future terabit networks based on space-division multiplexing (SDM) are discussed, and a coherent receiver utilizing joint digital signal processing (DSP) is demonstrated.
Abstract: We discuss the advantages of spatial superchannels for future terabit networks based on space-division multiplexing (SDM), and demonstrate reception of spatial superchannels by a coherent receiver utilizing joint digital signal processing (DSP). In a spatial superchannel, the SDM modes at a given wavelength are routed together, allowing a simplified design of both transponders and optical routing equipment. For example, common-mode impairments can be exploited to streamline the receiver's DSP. Our laboratory measurements reveal that the phase fluctuations between the cores of a multicore fiber are strongly correlated, and therefore constitute such a common-mode impairment. We implement master-slave phase recovery of two simultaneous 112-Gbps subchannels in a seven-core fiber, demonstrating reduced processing complexity with no increase in the bit-error ratio. Furthermore, we investigate the feasibility of applying this technique to subchannels carried on separate single-mode fibers, a potential transition strategy to evolve today's fiber networks toward future networks using multicore fibers.
127 citations
TL;DR: In this paper, a hole-assisted few-mode multicore fiber in which each core supports both the LP01 mode and the two degenerate LP11 modes has been designed and fabricated for the first time.
Abstract: A seven-core few-mode multicore fiber in which each core supports both the LP01 mode and the two degenerate LP11 modes has been designed and fabricated for the first time, to the best of our knowledge. The hole-assisted structure enables low inter-core crosstalk and high mode density at the same time. LP01 inter-core crosstalk has been measured to be lower than -60 dB/km. LP11 inter-core crosstalk has been measured to be around -40 dB/km using a different setup. The LP11 free-space excitation-induced crosstalk is simulated and analyzed. This fiber allows multiplexed transmission of 21 spatial modes per polarization per wavelength. Data transmission in LP01/LP11 mode over 1 km of this fiber has been demonstrated with negligible penalty.
TL;DR: In this article, a compact polarization beam splitter based on an asymmetrical Mach-Zehnder interferometer (MZI) on a sub-micron silicon-on-insulator platform is demonstrated experimentally.
Abstract: A compact polarization beam splitter based on an asymmetrical Mach-Zehnder interferometer (MZI) on a sub-micron silicon-on-insulator platform is demonstrated experimentally. The present MZI polarization beam splitter (PBS) is fabricated with a double-etching process and the deeply-etched region includes the MZI arms and the multimode- interference (MMI) couplers. In this way, the birefringence of the MZI arms and the power splitting ratio of the MMI coupler become insensitive to the etching depth, which makes the fabrication easier. The 2×2 MMI couplers are optimized to be polarization-insensitive and have a balanced ratio (50:50) for both polarizations. The measured extinction ratio of the fabricated MZI PBS is higher than 10 dB in the wavelength range from 1.54 to 1.58 μm.
TL;DR: In this article, a simple but accurate analytical model for the fiber-optic channel affected by cross-phase modulation (XPM) is proposed and validated through numerical simulations, which describes XPM as a time-varying and frequency-selective complex fading, whose impact and statistical properties can be analyzed.
Abstract: A simple but accurate analytical model for the fiber-optic channel affected by cross-phase modulation (XPM) is proposed and validated through numerical simulations. The model describes XPM as a time-varying and frequency-selective complex fading, whose impact and statistical properties can be analytically investigated. As an example, the proposed model is applied to derive an analytic lower bound to the channel capacity and to investigate the coherence properties of the channel.
TL;DR: Analysis of the decode-and-forward (DF) protocol in the free space optical (FSO) links following the Gamma-Gamma distribution and average bit error rate of the DF relaying is obtained.
Abstract: We analyze performance of the decode-and-forward (DF) protocol in the free space optical (FSO) links following the Gamma-Gamma distribution. The cumulative distribution function (cdf) and probability density function (pdf) of a random variable containing mixture of the Gamma-Gamma and Gaussian random variables is derived. By using the derived cdf and pdf, average bit error rate of the DF relaying is obtained.
TL;DR: In this paper, the authors demonstrate stable wavelength tunable inscription of polymer optical fiber Bragg gratings (FBGs) by straining the fiber during FBG inscription, and linearly tune the center wavelength over 7 nm with less than 1% strain.
Abstract: We demonstrate stable wavelength tunable inscription of polymer optical fiber Bragg gratings (FBGs). By straining the fiber during FBG inscription, we linearly tune the center wavelength over 7 nm with less than 1% strain. Above 1% strain, the tuning curve saturates and we show a maximum tuning of 12 nm with 2.25% strain. We use this inscription method to fabricate a dual-FBG strain sensor in a poly (methyl methacrylate) single-mode microstructured polymer optical fiber and demonstrate temperature compensated strain sensing around 850 nm.
TL;DR: In this article, a novel zigzag PN junction providing a modulation efficiency of 3.85× 10-5/V and a resistance-capacitance bandwidth of 51 GHz was proposed and demonstrated.
Abstract: We experimentally demonstrate silicon microring modulators with >;40-Gb/s modulation speed based on the carrier-depletion mechanism in reverse-biased PN junctions. A novel zigzag PN junction providing a modulation efficiency of 3.85× 10-5/V and a resistance-capacitance bandwidth of 51 GHz is proposed and demonstrated. The moderate Q factor of ~ 8000 and the operation wavelength detuning are optimized to relieve photon-lifetime-induced bandwidth limitation. Finally, with a voltage swing of 3 V, high-speed modulation of 20 and 44 Gb/s is experimentally demonstrated with the extinction ratio of 3.45 and 3.01 dB, showing great potential in the application of ultrahigh-capacity optical interconnects.
TL;DR: In this paper, an angle-tuned guided-mode resonance color filter is experimentally demonstrated, which exhibits blue, green, and red color responses at incident angles of 8 $^{circ}$, 20 $^{\circ}µ, and 35 $^µ$, respectively.
Abstract: A new angle-tuned guided-mode resonance color filter is experimentally demonstrated. The device is designed using numerical methods and patterned using laser interferometric lithography. It consists of a 55-nm-deep silicon nitride and air diffraction grating with a 270-nm grating period along with a 110-nm-thick silicon nitride waveguide layer deposited on a glass substrate. The fabricated filter exhibits blue, green, and red color responses at incident angles of 8 $^{\circ}$ , 20 $^{\circ}$ , and 35 $^{\circ}$ , respectively. It has a bandwidth of 10 nm with efficiency near 90%.
TL;DR: The main advantage of the proposed solution is that of avoiding the phase- ambiguity problem after a cycle slip, and for homogeneous transmission, the proposed scheme outperforms blind carrier recovery with differential decoding.
Abstract: A feedforward pilot-symbols-aided carrier-phase recovery scheme is described. The approach relies on pilot symbols that are time-division multiplexed with the transmitted data. In the scheme, an initial coarse estimation of the optical carrier phase, exploiting the knowledge of pilot symbols, is followed by a fine nondata-aided, or blind, estimation. The main advantage of the proposed solution is that of avoiding the phase- ambiguity problem after a cycle slip. The overhead and the impact on the performance of pilot symbols are investigated for long-haul transmission of 100-Gb/s polarization-multiplexed quadrature phase-shift keying wavelength-division-multiplexing signals in different scenarios. For homogeneous transmission, the proposed scheme outperforms blind carrier recovery with differential decoding.
TL;DR: In this paper, a photonic channelization scheme for a wideband radio-frequency (RF) signal based on an optical frequency comb (OFC), a comb filter, and an optical de-mux is proposed and demonstrated.
Abstract: A novel photonic channelization scheme for a wideband radio-frequency (RF) signal based on an optical frequency comb (OFC), a comb filter, and an optical de-mux is proposed and demonstrated. In the proposed channelizer, the input broadband RF signal is multicast by the OFC, spectrally sliced by a Fabry-Perot filter (FPF) and then channelized by a regular optical de-mux. Compared to previous proposals, the OFC can provide uniform and low-noise channelization and simplify the spectral alignment to the FPF. We demonstrate our scheme experimentally based on a 39-GHz-spaced OFC. As an application, instantaneous multiple-frequency measurement is demonstrated by directly detecting the channelized RF signal.
TL;DR: In this article, two fabrication-friendly apodization techniques that are compatible with deep UV lithography and can be used in mass-production of photonic-integrated circuits are presented.
Abstract: An accurate control of the apodization profile is still an issue for integrated Bragg grating filters fabricated in silicon-on-insulator because of the high modal confinement of these waveguides. In this letter, we present two fabrication-friendly apodization techniques that are compatible with deep UV lithography and can be used in mass-production of photonic-integrated circuits. These techniques are reliable even for weak effective index modulation amplitude, thus opening the door to the fabrication of long and elaborate grating structures.
TL;DR: A hybrid evanescently coupled III-V/silicon distributed feedback laser with an integrated monitor photodiode, based on adhesive divinyl siloxane-benzocyclobutene bonding and emitting at 1310 nm, is presented in this paper.
Abstract: A hybrid evanescently coupled III-V/silicon distributed-feedback laser with an integrated monitor photodiode, based on adhesive divinyl siloxane-benzocyclobutene bonding and emitting at 1310 nm, is presented. An output power of ~2.85 mW is obtained in a continuous wave regime at 10°C. The threshold current is 20 mA and a sidemode suppression ratio of 45 dB is demonstrated. Optical feedback is provided via corrugations on top of the silicon rib waveguide, while a specially developed bonding procedure yields 40-nm-thick adhesive bonding layers, enabling efficient evanescent coupling.
TL;DR: A method to separate and monitor the modes in real time is described as the basis of a method to measure the individual modal performance of a component during fabrication.
Abstract: The use of multimode fibers in mode division multiplexed space-division multiplexing systems offers one solution to the capacity limitations of single-mode fiber transmission. Passive components to control the individual modes in few-mode fiber (FMF) are key elements to build more complex modules and components necessary for a high performance system. Fiber-based mode converters are important elements in the FMF mux/demux, and long-period gratings have been investigated to provide mode conversion in two- and four-mode fibers. A method to separate and monitor the modes in real time is described as the basis of a method to measure the individual modal performance of a component during fabrication.
TL;DR: In this article, the authors present a compact all-fiberized erbium-doped fiber ring laser, which generates linearly polarized picosecond pulses with a maximum bandwidth of 135 nm and excellent spectral flatness.
Abstract: We present a compact all-fiberized erbium-doped fiber ring laser, which generates linearly polarized picosecond pulses with a maximum bandwidth of 135 nm and excellent spectral flatness. The pulse energy and width are reconfigurable from 0.7 to 1.1 nJ and from 6.5 to 220 ps, respectively, via controlling the pumping power and/or the cavity finesse. We also analyze the relative intensity noise (RIN) characteristics of the source that results in ${-}{\rm 97}~{\rm dB}$ at low frequencies (up to 100 kHz) and ${-}{\rm 104}~{\rm dB}$ at high frequencies (up to 5 MHz), respectively. In particular, the high-frequency RIN is attributed to the spontaneous Raman scattering generated in the laser and of a comparable level with that of a commercial supercontinuum source based on a mode-locked fiber laser.
TL;DR: In this paper, the authors report on coupling optics for connecting single-core singlemode fibers with multicore single-mode fibers, which enables the use of the same coupling device with a variety of multicore fibers whose structural parameters differ from one sample to another.
Abstract: In this letter, we report on coupling optics for connecting single-core single-mode fibers with multicore single-mode fibers. After a brief discussion of the options for such coupling systems, we describe our approach of using bulk optics to fabricate low-loss and low-crosstalk devices for both 7- and 19-core multicore fibers with the free-space design approach. This enables the use of the same coupling device with a variety of multicore fibers whose structural parameters differ from one sample to another. We present the results of experimental evaluations of these devices, discuss various causes of insertion loss, and analyze the coupling loss in detail.
TL;DR: In this paper, asymmetric Y-junctions have been used for spatial mode division multiplexing of polarization-maintaining, elliptical-core fiber data link, which could easily be extended to more modes.
Abstract: Spatial mode-division-multiplexing is seen as paramount to overcoming the bandwidth limitations of single-mode fiber. In this letter, spatial-multiplexing of polarization-maintaining, elliptical-core fiber is proposed using asymmetric Y-junctions. Asymmetric Y-junctions also allow for straightforward wavelength- and polarization-multiplexing. Numerical beam propagation method simulations are used to demonstrate the functioning of a three-mode elliptical-core fiber data link, which could easily be extended to more modes. The multiplexing of multiple spatial modes could potentially see multifold increases in fiber capacity.
TL;DR: In this article, the authors demonstrate a polarization rotator fabricated using a 4 etch-step complementary metal-oxide-semiconductor (CMOS)-compatible process including layer depositions on a silicon-on-insulator wafer.
Abstract: We demonstrate a polarization rotator fabricated using a 4 etch-step complementary metal-oxide-semiconductor (CMOS)-compatible process including layer depositions on a silicon-on-insulator wafer. The measured polarization rotation efficiency is over a wavelength range of 80 nm. A robustness investigation shows that the design is compatible with CMOS fabrication capabilities.
TL;DR: In this article, an ultrawide tunable microwave photonic notch filter with very high resolution is presented, which is based on a stimulated Brillouin scattering technique, which processes the modulation sidebands generated by a dual-drive Mach-Zehnder modulator.
Abstract: A new ultrawide tunable microwave photonic notch filter that exhibits a very high resolution is presented. It is based on a stimulated Brillouin scattering technique, which processes the modulation sidebands generated by a dual-drive Mach-Zehnder modulator. Tuning is realized by changing the drive frequency to an electro-optic intensity modulator. Experimental results demonstrate a high-resolution notch filter with a 3-dB bandwidth of 82 MHz, a notch depth of over 40 dB, a flat passband from near DC to 20 GHz with very low ripples, and a notch frequency that can be continuously tuned with shape invariance over an ultrawide frequency range from 2 to 20 GHz.
TL;DR: In this paper, a Ge/SiGe quantum well waveguide electroabsorption modulator that is monolithically integrated with silicon-on-insulator waveguides is reported.
Abstract: We report a Ge/SiGe quantum well waveguide electroabsorption modulator that is monolithically integrated with silicon-on-insulator waveguides The active quantum well section is selectively grown on a silicon-on-insulator substrate and has a footprint of 8 The integrated device demonstrates more than 32-dB contrast ratio with 1-V direct voltage swing at 35 GHz We also show the potential of this device to operate in the telecommunication C-band at room temperature
TL;DR: In this paper, the authors investigated a novel and ultracompact air-gap fiber Fabry-Perot interferometer (AG-FFPI), which is based on a polymer-filled hollow core fiber (HCF) endface.
Abstract: This letter, for the first time, investigates a novel, and ultracompact air-gap fiber Fabry-Perot interferometer (AG-FFPI), which is based on a polymer-filled hollow core fiber (HCF) endface. The proposed polymer-filled AG-FFPI has advantages of easy fabrication, high temperature sensitivity, low cost, and arbitrary length of air-gap. The variation of the Fabry-Perot cavity length can be greatly enhanced from exploiting the high thermal expansion coefficient of the elastic polymer-filled in the HCF. The proposed device exhibits a wavelength shift of the interference fringes that corresponds to temperature sensitivity of , which is equivalent to sensitivity to a change in cavity length of .
TL;DR: In this paper, a scheme using one intensity modulator and two phase modulators driven directly by sinusoidal waveform to generate an optical-frequency comb (OFC) is experimentally demonstrated.
Abstract: A scheme using one intensity modulator and two phase modulators driven directly by sinusoidal waveform to generate an optical-frequency comb (OFC) is experimentally demonstrated. It is relatively simple, where Bragg grating or specially tailored waveforms are not used. By setting the ratio of direct-current bias to half-wave voltage and phase shifts between sinusoidal waveform applied on the intensity and two phase modulators at appropriate values, 29 comb lines with spectral power variation less than 1.5 dB at 10 GHz are obtained. And the scheme has adjustability; a flat-top OFC with frequency spacing of 9.5-10 GHz is achieved.