1,479 research outputs found
Full-Field, Carrier-Less, Polarization-Diversity, Direct Detection Receiver based on Phase Retrieval
We realize dual-polarization full-field recovery using intensity only
measurements and phase retrieval techniques based on dispersive elements.
30-Gbaud QPSK waveforms are transmitted over 520-km standard single-mode fiber
and equalized from the receiver outputs using 2X2 MIMO
Mode-Multiplexed Transmission over Conventional Graded-Index Multimode Fibers
We present experimental results for combined mode-multiplexed and wavelength multiplexed transmission over conventional graded-index multimode fibers. We use mode-selective photonic lanterns as mode couplers to precisely excite a subset of the modes of the multimode fiber and additionally to compensate for the differential group delay between the excited modes. Spatial mode filters are added to suppress undesired higher order modes. We transmit 30-Gbaud QPSK signals over 60 WDM channels, 3 spatial modes, and 2 polarizations, reaching a distance of 310 km based on a 44.3 km long span. We also report about transmission experiments over 6 spatial modes for a 17-km single-span experiment. The results indicate that multimode fibers support scalable mode-division multiplexing approaches, where modes can be added over time if desired. Also the results indicate that mode-multiplexed transmission distance over 300 km are possible in conventional multimode fibers
Laguerre-Gaussian mode sorter
Light's spatial properties represent an infinite state space, making it
attractive for applications requiring high dimensionality, such as quantum
mechanics and classical telecommunications, but also inherently spatial
applications such as imaging and sensing. However, there is no demultiplexing
device in the spatial domain comparable to a grating or calcite for the
wavelength and polarisation domains respectively. Specifically, a simple device
capable of splitting a finite beam into a large number of discrete spatially
separated spots each containing a single orthogonal spatial component. We
demonstrate a device capable of decomposing a beam into a Cartesian grid of
identical Gaussian spots each containing a single Laguerre-Gaussian component.
This is the first device capable of decomposing the azimuthal and radial
components simultaneously, and is based on a single spatial light modulator and
mirror. We demonstrate over 210 spatial components, meaning it is also the
highest dimensionality mode multiplexer of any kind
Dual Polarization Full-Field Signal Waveform Reconstruction Using Intensity Only Measurements for Coherent Communications
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
White Gaussian Noise Based Capacity Estimate and Characterization of Fiber-Optic Links
We use white Gaussian noise as a test signal for single-mode and multimode
transmission links and estimate the link capacity based on a calculation of
mutual information. We also extract the complex amplitude channel estimations
and mode-dependent loss with high accuracy.Comment: submitted to The Optical Networking and Communication Conference
(OFC) 201
Dual-Comb Swept Wavelength Interferometry
We demonstrate a hybrid swept wavelength interferometry-dual-comb spectroscopy system for fast broadband full-field measurements. Phase and amplitude retrieval is experimentally verified and compensation of laser sweep nonlinearity is demonstrated without external referencing
Analysis of inter-core cross-gain modulation in cladding pumped multi-core fiber amplifiers
We numerically investigate pump-induced gain variations in eight-core fi ber amplifi ers. We compare two fi bers with different erbium profi les by
varying input power from -25 dBm to 0 dBm in one or four cores. Inter-core cross-gain modulation is < 0.6 dB
Modeling and characterization of cladding-pumped erbium-ytterbium co-doped fibers for amplification in communication systems
Cladding-pumped optical fiber amplifiers are of increased interest in the context of space-division multiplexing but are known to suffer from low power efficiency. In this context, ytterbium (Yb) co-doping can be an attractive solution to improve the performance of erbium (Er) doped fiber amplifiers. We present a detailed direct comparison between Er/Yb-co-doping and Er-doping using numerical simulations validated by experimental results. Two double-cladding fibers, one doped with Er only and the other one co-doped with Er and Yb, were designed, fabricated and characterized. Using the experimentally extracted parameters, we simulate multi-core fiber amplifiers and investigate the interest of Er/Yb-co-doping. We calculate the minimum gain of the amplifiers over a 35-nm spectral window considering various scenarios
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