Showing papers on "Polarization mode dispersion published in 2019"
TL;DR: A methodology to calculate the coupling strength between OAM mode groups due to fiber perturbations is provided and it is found that birefringence causes the highest modal crosstalk because it strongly couples groups with a lower propagation-constant mismatch.
Abstract: After briefly recalling the issue of OAM mode purity in strongly-guiding ring-core fibers, this paper provides a methodology to calculate the coupling strength between OAM mode groups due to fiber perturbations. The cases of stress birefringence and core ellipticity are theoretically and numerically investigated. It is found that both perturbations produce the same coupling pattern among mode groups, although with different intensities. The consequence is that birefringence causes the highest modal crosstalk because it strongly couples groups with a lower propagation-constant mismatch. The power coupling to parasitic TE and TM modes is also quantified for both perturbations and is found to be non-negligible. Approximate modal crosstalk formulas valid for weakly-guiding multi-core fibers, but whose parameters are adapted to the present case of strongly guiding OAM fibers, are found to provide a reasonable fit to numerical results. Finally, the effect that modal coupling has on OAM transmission is assessed in terms of SNR penalty.
37 citations
TL;DR: This work proposes a self-compensating polarization encoder based on a lithium niobate phase modulator inside a Sagnac interferometer and implements it using only commercial off-the-shelf (COTS) components.
Abstract: Quantum key distribution (QKD) allows distant parties to exchange cryptographic keys with unconditional security by encoding information on the degrees of freedom of photons. Polarization encoding has been extensively used for QKD along free-space, optical fiber, and satellite links. However, the polarization encoders used in such implementations are unstable, expensive, and complex and can even exhibit side channels that undermine the security of the protocol. Here we propose a self-compensating polarization encoder based on a lithium niobate phase modulator inside a Sagnac interferometer and implement it using only commercial off-the-shelf (COTS) components. Our polarization encoder combines a simple design and high stability reaching an intrinsic quantum bit error rate as low as 0.2%. Since realization is possible from the 800 to the 1550 nm band using COTS devices, our polarization modulator is a promising solution for free-space, fiber, and satellite-based QKD.
36 citations
TL;DR: The error-free SKGD scheme is realized in fiber channel using the information reconciliation (IR) technology, where Bose-Chaudhuri-Hocquenghem (BCH) codes are applied and analyzed and verified against the possible fiber-tapping attacks.
Abstract: This paper proposes and experimentally demonstrates an error-free secure key generation and distribution (SKGD) scheme in classical optical fiber link by exploiting Stokes parameters (SPs) of the state of polarization (SOP). Due to the unique birefringence distribution of the optical fiber channel, random but high-correlated SPs are shared between Alice and Bob. The dynamic SPs are also affected by the time-varying environmental factors, providing the source of randomness for the secret key extraction. As a proof of concept, key generation rate (KGR) of 213-bits/s is successfully demonstrated over 25-km standard single-mode fiber (SSMF). The error-free SKGD is realized in fiber channel using the information reconciliation (IR) technology, where Bose-Chaudhuri-Hocquenghem (BCH) codes are applied. Due to the channel uniqueness and the high-sensitivity to the initial SOP of optical signals, high-level security is provided by the proposed scheme, which is analyzed and verified against the possible fiber-tapping attacks. Moreover, the proposed SKGD scheme offers additional benefits such as simple structure, low cost, and suitablity for long-haul transmission.
35 citations
TL;DR: This high-speed intrinsically stable polarization modulation scheme based on an inherently stable Sagnac interferometer is reported, which can be widely applied to many polarization-encoding QKD systems, such as BB84, MDI, etc.
Abstract: Polarization modulation plays a key role in polarization-encoding quantum key distribution (QKD). Here, we report a new, to the best of our knowledge, polarization modulation scheme based on an inherently stable Sagnac interferometer. The presented scheme is free of polarization mode dispersion and calibration as well as insensitive to environmental influences. Successful experiments at a repetition frequency of 1.25 GHz have been conducted to demonstrate the feasibility and stability of the scheme. The measured average quantum bit-error rate of the four polarization states is as low as 0.27% for 80 consecutive minutes without any adjustment. This high-speed intrinsically stable polarization modulation can be widely applied to many polarization-encoding QKD systems, such as BB84, MDI, etc.
34 citations
TL;DR: The transmission of 100 Gbit/s and beyond vestigial sideband (VSB) n-level pulse amplitude modulation (PAM-n) signals, with a commercial 10 GHz-class directly modulated laser (DML) in the C-band, using optical filtering is experimentally demonstrated.
Abstract: We experimentally demonstrate the transmission of 100 Gbit/s and beyond vestigial sideband (VSB) n-level pulse amplitude modulation (PAM-n) signals, with a commercial 10 GHz-class directly modulated laser (DML) in the C-band, using optical filtering. To mitigate transmission impairments at the transmitter side, Nyquist pulse shaping and Kaiser Window filtering techniques are used to overcome the limited bandwidth of optoelectronic devices. At the receiver side, the joint nonlinear equalization based on cascaded multi-modulus algorithm (CMMA) and Volterra Filter (VF) is used to reduce the strong nonlinear impairments from chirp and chromatic dispersion (CD). 100 Gb/s PAM-4, 107.5 Gb/s PAM-4, and 101.25 Gb/s PAM-8 signals can be successfully transmitted over 45 km, 10 km and 10 km standard single-mode fiber (SSMF) under the bit-error-ratio (BER) of 3.8 × 10-3, respectively.
31 citations
TL;DR: In this paper, a particle method for the computation of the resulting achievable information rate and spectral efficiency (SE) is presented and employed to lower-bound the channel capacity, and the dependence of the SE on the link length, amplifier spacing, and presence or absence of in-line dispersion compensation is studied.
Abstract: After reviewing models and mitigation strategies for interchannel nonlinear interference (NLI), we study its characteristics and coherence properties. Based on this study, we devise an NLI mitigation strategy, which exploits the synergic effect of phase and polarization noise (PPN) compensation and subcarrier multiplexing with symbol-rate optimization. This synergy persists even for high-order modulation alphabets and Gaussian symbols. A particle method for the computation of the resulting achievable information rate and spectral efficiency (SE) is presented and employed to lower-bound the channel capacity. The dependence of the SE on the link length, amplifier spacing, and presence or absence of in-line dispersion compensation is studied. Single-polarization and dual-polarization scenarios with either independent or joint processing of the two polarizations are considered. Numerical results show that, in links with ideal distributed amplification, an SE gain of about 1 bit/s/Hz/polarization can be obtained (or, in alternative, the system reach can be doubled at a given SE) with respect to single-carrier systems without PPN mitigation. The gain is lower with lumped amplification, increases with the number of spans, decreases with the span length, and is further reduced by in-line dispersion compensation. For instance, considering a dispersion-unmanaged link with lumped amplification and an amplifier spacing of 60 km, the SE after 80 spans can be be increased from 4.5 to 4.8 bit/s/Hz/polarization, or the reach raised up to 100 spans (+25%) for a fixed SE.
27 citations
03 Mar 2019
TL;DR: A novel, two-stage algorithm for polarization demultiplexing and equalization of probabilistically shaped QAM is presented, requiring no knowledge of the channel or transmitted sequence.
Abstract: A novel, two-stage algorithm for polarization demultiplexing and equalization of probabilistically shaped QAM is presented. It operates blindly, requiring no knowledge of the channel or transmitted sequence. Performance is validated under realistic PMD conditions.
26 citations
TL;DR: A new Kalman filter structure is proposed, which can jointly compensate ultra-fast RSOP, large PMD and RCD, and compared with CMA/MMA, the proposed Kalman scheme can provide a significant performance enhancement.
Abstract: Polarization demultiplexing is generally carried out by a multiple-input multiple-output (MIMO) based algorithm in polarization division multiplexing (PDM) coherent systems. However, in some extreme environments, the MIMO algorithm becomes inapplicable due to the ultra-fast rotation of the state of polarization (RSOP) and large polarization mode dispersion (PMD). In addition, the residual chromatic dispersion (RCD) is always present because of the mismatch of the compensated chromatic dispersion and real value induced in the optical fiber channel. According to the literature, the Kalman filter-based polarization demultiplexing algorithms possess very weak RCD tolerance. Faced with this dilemma, in this paper, a new Kalman filter structure is proposed, which can jointly compensate ultra-fast RSOP, large PMD and RCD. This Kalman filter structure enables the equalization of the RSOP in the time domain and compensation for RCD and PMD in the frequency domain. We verified the performance of the proposed Kalman scheme in the 28 Gbaud PDM-QPSK/16 QAM coherent system, with a comparison to constant modulus algorithm/multiple modulus algorithm (CMA/MMA). The simulation results confirm that, compared with CMA/MMA, the proposed Kalman scheme can provide a significant performance enhancement to cope with ultra-fast RSOP (up to 3 Mrad/s) and large PMD (more than 200 ps) with a large tolerance to RCD (over the range of ± 820 ps/nm in PDM-QPSK and ± 500 ps/nm in PDM-16 QAM).
22 citations
TL;DR: Simulation results show that the proposed technique plays a key role in dispersion mitigation in multi-channel optical transmission to uphold multi-Gb/s transmission and bit error rate (BER) and quality factor (Q-factor) below 10 − 5 and above 5, respectively, are achieved with electrical domain equalizers for the OCN in the presence of multiple distortion effects showing the effectiveness of the proposed adaptive equalization techniques.
Abstract: Optical communication networks (OCNs) provide promising and cost-effective support for the ultra-fast broadband solutions, thus enabling them to address the ever growing demands of telecommunication industry such as high capacity and end users’ data rate. OCNs are used in both wired and wireless access networks as they offer many advantages over conventional copper wire transmission such as low power consumption, low cost, ultra-high bandwidth, and high transmission rates. Channel effects caused by light propagation through the fiber limits the performance, hence the data rate of the overall transmission. To achieve the maximum performance gain in terms of transmission rate through the OCN, an optical downlink system is investigated in this paper using feed forward equalizer (FFE) along with decision feedback equalizer (DFE). The simulation results show that the proposed technique plays a key role in dispersion mitigation in multi-channel optical transmission to uphold multi-Gb/s transmission. Moreover, bit error rate (BER) and quality factor (Q-factor) below 10 − 5 and above 5, respectively, are achieved with electrical domain equalizers for the OCN in the presence of multiple distortion effects showing the effectiveness of the proposed adaptive equalization techniques.
21 citations
TL;DR: A theoretical model is presented describing how the magnitude and orientation of polarization dependent loss (PDL), a common impairment in fiber-optic networks, affects the entanglement quality of distributed quantum states.
Abstract: Quantum networking brings together several diverse research areas, such as fiber-optic communication, quantum optics, and quantum information, to achieve capabilities in security, secret sharing, and authentication which are unavailable classically. The development of practical fiber-based quantum networks requires an understanding of the reach, rates, and quality of the entanglement of distributed quantum states. Here, we present a theoretical model describing how the magnitude and orientation of polarization dependent loss (PDL), a common impairment in fiber-optic networks, affects the entanglement quality of distributed quantum states. Furthermore, we theoretically characterize how PDL in one fiber channel can be optimally applied in order to nonlocally compensate for the PDL present in another channel. We present experimental results that verify our theoretical model.
21 citations
TL;DR: A novel polarization-insensitive arrayed waveguide grating (AWG) built with silicon nitride waveguides is presented in this Letter and a 100 GHz 1×8 wavelength-division multiplexer with crosstalk levels below -16 dB is demonstrated experimentally.
Abstract: Next-generation passive optical networks require integrated, polarization-insensitive wavelength-division multiplexing solutions, for which the recently emerging low-loss silicon nitride nanophotonic platforms hold great potential. A novel polarization-insensitive arrayed waveguide grating (AWG) built with silicon nitride waveguides is presented in this Letter. Polarization insensitivity is obtained when both the channel spacing and the center wavelength of the two orthogonal polarization states (i.e., the TE and TM waveguide modes) are simultaneously aligned. In our design, the channel spacing alignment between the polarization states is obtained by optimizing the geometry of the arrayed waveguides, whereas the central wavelength polarization insensitivity is obtained by splitting the two polarization states and adjusting their angle of incidence at the input star coupler to compensate for the polarization mode dispersion of the AWG. A 100 GHz 1×8 wavelength-division multiplexer with crosstalk levels below −16 dB is demonstrated experimentally.
TL;DR: A simultaneous threefold modal and wavelength conversion process of a 10-Gbit/s On/Off keying signal in a 1.8-km long graded-index 6-LP-mode fiber based on a phase-matched inter-modal four-wave mixing phenomenon occurring between the fundamental mode and 3 higher-order modes of the fiber is demonstrated.
Abstract: We demonstrate experimentally a simultaneous threefold modal and wavelength conversion process of a 10-Gbit/s On/Off keying signal in a 1.8-km long graded-index 6-LP-mode fiber. The principle of operation is based on a phase-matched inter-modal four-wave mixing phenomenon occurring between the fundamental mode and 3 higher-order modes of the fiber. The converted signals show well-opened eye-diagrams and error-free processing.
TL;DR: This work presents a full-field measurement technique using only direct detection that does not require any beating with a strong carrier LO, and proposes phase retrieval algorithms based on alternating projections that makes use of dispersive elements, allowing to recover the optical phase from intensity-only measurements.
Abstract: Conventional optical coherent receivers capture the full electrical field, including amplitude and phase, of a signal waveform by measuring its interference against a stable continuous-wave local oscillator (LO). In optical coherent communications, powerful digital signal processing (DSP) techniques operating on the full electrical field can effectively undo transmission impairments such as chromatic dispersion (CD), and polarization mode dispersion (PMD). Simpler direct detection techniques do not have access to the full electrical field and therefore lack the ability to compensate for these impairments. We present a full-field measurement technique using only direct detection that does not require any beating with a strong carrier LO. Rather, phase retrieval algorithms based on alternating projections that makes use of dispersive elements are discussed, allowing to recover the optical phase from intensity-only measurements. In this demonstration, the phase retrieval algorithm is a modified Gerchberg Saxton (GS) algorithm that achieves a simulated optical signal-to-noise ratio (OSNR) penalty of less than 4dB compared to theory at a bit-error rate of 2 times 10-2. Based on the proposed phase retrieval scheme, we experimentally demonstrate signal detection and subsequent standard 2x2 multiple-input-multiple-output (MIMO) equalization of a polarization-multiplexed 30-Gbaud QPSK transmitted over a 520-km standard single-mode fiber (SMF) span.
TL;DR: The potential of online performance assessment by leveraging bandwidth-variable transponders in flexible optical networks, and its benefit by simulating the total capacity of typical long-haul networks, is discussed.
Abstract: Awareness of optical network performance and its accurate prediction enable squeezing of margins allocated for stable operation. We discuss the potential of online performance assessment by leveraging bandwidth-variable transponders in flexible optical networks, and quantify its benefit by simulating the total capacity of typical long-haul networks. An experimental analysis in a system lab and a field trial demonstrate the viability and remarkable accuracy of the presented technologies in a live network. Finally, we analyze the impact of disaggregated networks on performance awareness.
TL;DR: A Hilbert-transform-based broadband chromatic dispersion (CD) compensation scheme for radio-over-fiber links is proposed and experimentally demonstrated, which significantly improves the third-order spurious-free dynamic range.
Abstract: A Hilbert-transform-based broadband chromatic dispersion (CD) compensation scheme for radio-over-fiber links is proposed and experimentally demonstrated. By constructing a Hilbert transform path, CD-induced phase shifts, which initially lead to periodic power fading of the output RF signals, are transferred to the phases of the RF signals. As a result, the powers of the output RF signals are free from the effect of CD in a broadband frequency range. Experimental results show that a flat normalized amplitude-frequency response is actualized within 2–24 GHz, with only 3.02 dB/4.27 dB power fluctuation after transmission over an equivalent of a 38.6 km/43.6 km single-mode fiber. Besides, compared with a conventional dispersive path, the proposed CD compensation scheme significantly improves the third-order spurious-free dynamic range by 23.60 dB.
TL;DR: In this article, the effects of polarization mode dispersion (PMD) in systems with double polarizations were compensated using pre-and post-compensation. And the results were achieved by implementing polarization controllers, polarization beam combiners and splitters.
Abstract: 5G mobile networks targets wireless connection capacity up to 10 Gb/s. For this purpose, we propose a method to considerably increase capacity. In this paper first, we show how to compensate the effects of polarization mode dispersion (PMD) in systems with double polarizations where PMD in such systems could cause fluctuations in optical transmission due to crosstalk and cross phase modulation. Second, we show how to enhance system capacity benefiting from polarization multiplexing (POL-MUX) technique which can provide double bandwidth efficiency. Based on the simulation results, we have achieved optimum system performance and we were able to reduce the PMD effect using pre- and post-compensation. We also have improved the POL-MUX technique using coherent detection in case of 16/64 QAM modulations. The results were achieved by implementing polarization controllers, polarization beam combiners and splitters, as well as polarization phase shifters.
TL;DR: The results show that the system can protect the key distribution under different attacks, attributed to wideband optical noise and asymmetric MZI structures, and is compatible with the existing optical fiber communication infrastructure.
Abstract: We propose and experimentally demonstrate an approach to generate and distribute secret keys over optical fiber communication infrastructure. Mach-Zehnder interferometers (MZIs) are adopted for key generation by transferring the environmental noise to random optical signals. A novel combination of wideband optical noise and an asymmetric MZI structure enables the secret keys to be securely transmitted and exchanged over public fiber links without being detected. We experimentally demonstrate this system and show reliable performance: keys are generated at the rate of 502 bit/s, and are successfully exchanged between two parties over a 10 km optical fiber with a bit error of ∼ 0.3%. System security analysis is performed by corroborating our experimental findings with simulations. The results show that our system can protect the key distribution under different attacks, attributed to wideband optical noise and asymmetric MZI structures. Compared to the previous schemes based on distributed MZIs, our scheme exploits localized MZI which provides twofold advantages. Firstly, the key generation rate can be increased by a factor of 5.7 at a negligible additional cost. Secondly, the system becomes robust to, in particular, active intrusion attack. The proposed system is a reliable and cost-effective solution for key establishment, and is compatible with the existing optical fiber communication infrastructure.
TL;DR: A loss weight adaptive multi-task learning based artificial neural network (MTL-ANN) is applied for joint optical signal-to-noise ratio (OSNR) monitoring and modulation format identification (MFI) and results show that the MFI accuracy reaches 100% in the estimated OSNR range.
Abstract: A loss weight adaptive multi-task learning based artificial neural network (MTL-ANN) is applied for joint optical signal-to-noise ratio (OSNR) monitoring and modulation format identification (MFI). We conduct an experiment of polarization division multiplexing (PDM) coherent optical system with 5 km standard single mode fiber (SSMF) transmission to verify this monitor. A group of modulation schemes including nine modulation adaptive M-QAM formats are selected as the transmission signals. Instead of circular constellation, signals’ amplitude histograms after constant module algorithm (CMA) based polarization de-multiplexing are selected as input features for our proposed monitor. The experimental results show that the MFI accuracy reaches 100% in the estimated OSNR range. Furthermore, when treated as regression problem and classification problem, OSNR estimation with a root mean-square error (RMSE) of 0.68 dB and an accuracy of 98.7% are achieved, respectively. Unlike loss weight fixed MTL-ANN, loss weight adaptive MTL-ANN could search the optimal loss weight ratio automatically for different link configurations. Besides that, the number of estimated parameters can be easily expanded, which is attractive for multiple parameters estimation in future heterogeneous optical networks.
27 Feb 2019
TL;DR: In this paper, the authors show that Raman scattering among orbital angular momentum (OAM) modes in optical fibers has similar properties and experimentally characterize Raman gain among OAM modes in a fiber supporting multiple OAM mode for both the pump and signal.
Abstract: Raman scattering among conventional linearly polarized (LP) modes in single mode optical fibers is generally accepted as a promising way to achieve distributed amplification due to the fact that Raman amplification may provide gain at any wavelength, determined by the used pump wavelength, and excellent noise performance. Here, we show that Raman scattering among orbital angular momentum (OAM) modes in optical fibers have similar properties. We show theoretically that the Raman gain among OAM modes is independent on the topological charge of the OAM modes and that the gain efficiency when the pump and signal are parallel (orthogonally) polarized is similar to the Raman scattering among LP modes in parallel (orthogonal) states of polarization. In addition, we experimentally characterize Raman gain among OAM modes in a fiber supporting multiple OAM modes for both the pump and signal. Finally, we discuss the impact of polarization mode dispersion.
03 Mar 2019
TL;DR: The INTREPID program is developing power efficient coherent optics for package-level integration with future switch ICs as a path to realizing higher-radix switches for flatter networks while enabling new architectures incorporating optical routing and switching.
Abstract: The INTREPID program is developing power efficient coherent optics for package-level integration with future switch ICs as a path to realizing higher-radix switches for flatter networks while enabling new architectures incorporating optical routing and switching.
TL;DR: In this paper, the impact of polarization mode dispersion (PMD) on the single-polarization signal transmission over the continuous spectrum (CS) of a long-haul optical fiber link defined by nonlinear Fourier transform (NFT) is studied.
Abstract: The impact of polarization mode dispersion (PMD) is studied on the single-polarization signal transmission over the continuous spectrum (CS) of a long-haul optical fiber link defined by nonlinear Fourier transform (NFT). It is shown that a linear all-order PMD compensation can reverse most of PMD effects in the temporal domain. However, due to the nonlinear interaction of the two polarization modes, the CS is distorted in the nonlinear spectral domain. Simulation results are presented, and a perturbation model is proposed based on the simulation results to describe the impact of PMD for different modulation formats and fiber parameters. It is demonstrated that, after linear PMD compensation, the residual polarization-dependent effects generate a constellation rotation and additional noise in the nonlinear spectral domain. The performance of NFT-based system in the presence of both PMD and amplifier noise is also studied. The results show that the effect of PMD is small provided that an efficient linear PMD compensation is performed in time domain.
01 Jan 2019
TL;DR: In this article, the authors show that carefully designed multi-step approaches can lead to better performance-complexity trade-offs than their few-step counterparts, and they propose a multi-stage approach to compensate for fiber nonlinearity.
Abstract: For the efficient compensation of fiber nonlinearity, one of the guiding principles appears to be: fewer steps are better and more efficient. We challenge this assumption and show that carefully designed multi-step approaches can lead to better performance-complexity trade-offs than their few-step counterparts.
03 Mar 2019
TL;DR: To meet the eMBB challenges in 5G, this work has systematically explored the potential of the photonics-aided mm-wave communication in terms of the wireless transmission capacity and distance it can accommodate and has realized the record-breaking product of wireless transmissioncapacity and distance.
Abstract: To meet the eMBB challenges in 5G, we have systematically explored the potential of the photonics-aided mm-wave communication in terms of the wireless transmission capacity and distance it can accommodate. Enabled by various kinds of advanced techniques and devices, we have successfully achieved the significant enhancement of the wireless transmission capacity from 100Gb/s to 400Gb/s, even to 1Tb/s, and we also have realized the record-breaking product of wireless transmission capacity and distance, i.e., 54Gb/s×2.5km.
TL;DR: The simulation and experiment results demonstrate that the proposed adaptive Kalman filter scheme has a stable and better performance of the equalization for large PMD combined with ultrafast RSOP, with a greater tolerance the to time-varying extreme polarization environments than that using the extended Kalman filters adopted in the previous work.
TL;DR: In this paper, a new method to monitor the optical signal-to-noise rate (OSNR) for 112-Gb/s non-return to zero polarization-division-multiplexed quadrature phase-shift keying systems, using support vector regression trained with Stokes parameters, was proposed.
Abstract: We proposed a new method to monitor the optical signal-to-noise rate (OSNR) for 112-Gb/s non-return-to-zero polarization-division-multiplexed quadrature phase-shift keying systems, using support vector regression trained with Stokes parameters. The numerical simulations show that OSNR levels between 11 and 35 dB can be estimated within ±1 dB with the interference of chromatic dispersion, polarization mode dispersion, and polarization-dependent loss.
03 Mar 2019
TL;DR: This work considers methods for containment of the effects of optical nonlinearities in coherent optical transmission and distinguished according to their practicality and effectiveness.
Abstract: We consider methods for containment of the effects of optical nonlinearities in coherent optical transmission. These are distinguished according to their practicality and effectiveness.
TL;DR: It is shown that HCF links enable the positioning error to be reduced down to the centimeter level even when subject to tens of degrees Celsius temperature variations, a 20-fold improvement over standard single mode fiber systems which would require active compensation schemes to achieve similar levels of time synchronization accuracy.
Abstract: Positioning accuracy in 5G networks (achieved via techniques based on observed time difference of arrival (OTDoA)) is limited by the synchronization error between the cellular base stations. Here, we demonstrate that these base stations can be synchronized entirely passively through the use of emerging forms of hollow core fiber (HCF) as the data transmission medium in the 5G front-haul network. This is possible due to the excellent thermal stability of HCF which allows the synchronization error among cellular base stations to be reduced significantly as compared to systems based on standard single mode fibers. Reducing this synchronization error is necessary to meet the strict timing requirements envisaged for 5G networks. We analyze the polarization mode dispersion, chromatic dispersion, and thermal stability of the HCF and give suggestions on how to use the HCF to balance overall radio over fiber (RoF) link performance in 5G front-haul networks. In a proof of concept experiment we show that HCF links enable the positioning error (calculated with the OTDoA method) to be reduced down to the centimeter level even when subject to tens of degrees Celsius temperature variations. This represents a 20-fold improvement over standard single mode fiber systems which would require active compensation schemes to achieve similar levels of time synchronization accuracy.
TL;DR: It is shown that the transfer of the Belinfante momentum to particles in the evanescent field of waveguides depends in a non-trivial way on the polarization state of light within that waveguide, allowing for a minimally invasive method to probe the polarization within a photonic chip.
Abstract: Current day high speed optical communication systems employ photonic circuits using platforms such as silicon photonics. In these systems, the polarization state of light drifts due to effects such as polarization mode dispersion and nonlinear phenomena generated by photonic circuit building blocks. As the complexity, the number, and the variety of these building blocks grows, the demand increases for an in-situ polarization determination strategy. Here, we show that the transfer of the Belinfante momentum to particles in the evanescent field of waveguides depends in a non-trivial way on the polarization state of light within that waveguide. Surprisingly, we find that the maxima and minima of the lateral force are not produced with circularly polarized light, corresponding to the north and south poles of the Poincare sphere. Instead, the maxima are shifted along the great circle of the sphere due to the phase differences between the scattered TE and TM components of light. This effect allows for an unambiguous reconstruction of the local polarization state of light inside a waveguide. Importantly, this technique depends on interaction with only the evanescent tails of the fields, allowing for a minimally invasive method to probe the polarization within a photonic chip.
TL;DR: A polarization-sensitive (PS) extension for bright- and dark-field (BRAD) optical coherence tomography imaging is presented and two phantoms consisting of different-sized microparticles and a brain tissue specimen were imaged to demonstrate the complementary image contrast.
Abstract: We present a polarization-sensitive (PS) extension for bright- and dark-field (BRAD) optical coherence tomography imaging. Using a few-mode fiber detection scheme, the light backscattered at different angles is separated, and the BRAD images of tissue scattering are generated. A calibration method to correct for the fiber birefringence is proposed. Since particle scattering profiles are polarization dependent, a PS detection extends the capabilities for investigating the scattering properties of biological tissues. Both phantoms consisting of different-sized microparticles and a brain tissue specimen were imaged to validate the system performance and demonstrate the complementary image contrast.
TL;DR: Simulations based on a 28 Gbaud polarization division multiplexed quadrature-phase shift keying coherent optical communication system show that the proposed two-stage Kalman scheme comprehensively outperforms the CMA-IMP-BPS scheme in solving the problems of RSOP, PMD, rCD, CFO, and CPN.