Giant tunable optical dispersion using chromo-modal excitation of a multimode waveguide

Diebold, Eric D.; Hon, Nick K.; Zhang, Tan; Chou, Jason; Sienicki, Todd; Wang, Chao; Jalali, Bahram

doi:10.1364/oe.19.023809

Cited by 54 publications

(29 citation statements)

References 34 publications

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“…Despite extensive theoretical and simulation studies on the AST approach including this work, quite little experimental study on this topic has been reported so far, mainly due to the lack of good optical filter offering an engineered group delay or dispersion profile. Potential good candidates to achieve the particularly designed AST filter include customized fibre Bragg gratings [14,22,23], chromo-modal dispersion mechanism [24] with the aid of mode-selective excitation [25], and photonic crystal fibre (PCF) with precisely controlled chromatic dispersion profile [26].…”

Section: Discussionmentioning

confidence: 99%

Adaptive non-uniform photonic time stretch for blind RF signal detection with compressed time-bandwidth product

Mididoddi

Wang

2017

Optics Communications

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Photonic time stretch significantly extends the effective bandwidth of existing analog-to-digital convertors by slowing down the input high-speed RF signals. Non-uniform photonic time stretch further enables time bandwidth product reduction in RF signal detection by selectively stretching high-frequency features more. However, it requires the prior knowledge of spectral-temporal distribution of the input RF signal and has to reconfigure the time stretch filter for different RF input signals. Here we propose for the first time an adaptive non-uniform photonic time stretch method based on microwave photonics prestretching that achieves blind detection of high-speed RF signals with reduced time bandwidth product. Non-uniform photonic time stretch using both quadratic and cubic group delay response has been demonstrated and time bandwidth product compression ratios of 72% and 56% have been achieved respectively.

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Section: Discussionmentioning

confidence: 99%

Adaptive non-uniform photonic time stretch for blind RF signal detection with compressed time-bandwidth product

Mididoddi

Wang

2017

Optics Communications

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“…For each experiment the source spectral width is measured with an optical spectrum analyzer and converted to coherence time t c . To excite a large number of modes we overfill the acceptance angle of the MMF by tightly focusing the initially fully spatially coherent light on the input face of the MMF [25]. The position of the focus is not centered on the core of the MMF in order to excite all possible skew rays in the fiber.…”

Section: Methodsmentioning

confidence: 99%

Spatial coherence at the output of multimode optical fibers

Efimov¹

2014

Opt. Express

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The modulus of the complex degree of coherence is directly measured at the output of a step-index multimode optical fiber using lateral-sheering, delay-dithering Mach-Zehnder interferometer. Pumping the multimode fiber with monochromatic light always results in spatially-coherent output, whereas for the broadband pumping the modal dispersion of the fiber leads to a partially coherent output. While the coherence radius is a function of the numerical aperture only, the residual coherence outside the main peak is an interesting function of two dimensionless parameters: the number of non-degenerate modes and the ratio of the modal dispersion to the coherence time of the source. We develop a simple model describing this residual coherence and verify its predictions experimentally.

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“…7b) [32], [33], the ChromoModal Dispersion (CMD) device (Fig. 7c) [34], and the reconfigurable optical add-drop multiplexers (ROADMs) [35], [36]. The CFBG is a distributed Bragg reflector (periodic variation in the refractive index) written in a short segment of an optical fiber that reflects particular wavelengths of light and transmits all others (Fig.…”

Section: Optical Implementations and Reconfigurabilitymentioning

confidence: 99%

“…The CMD is a type of dispersive device that converts the large modal (spatial) dispersion inherent in multi-mode fibers or waveguide to chromatic (frequency dependent) dispersion ( Fig. 7c) [34]. It does so by combining the waveguide with a diffraction grating.…”

Section: Optical Implementations and Reconfigurabilitymentioning

confidence: 99%

Tailoring Wideband Signals With a Photonic Hardware Accelerator

Jalali

Mahjoubfar

2015

Proc. IEEE

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| Digital hardware accelerators are increasingly employed to speed up computation and reduce power dissipation, enabling real-time operation. Inspired by this paradigm, we propose the concept of the photonic hardware acceleratorVan analog optical processing engine that precedes optical-to-electrical conversion and alleviates the burden on subsequent electronics. We propose one specific class of photonic hardware accelerators designed to assist in acquisition, feature extraction, and storage of wideband waveforms.This fundamental unit reshapes, in real time, the spectrotemporal evolution of a wideband streaming signal based on signal's sparsity. Functioning as an information gearbox, the accelerator transforms the signal according to the nonuniform entropy of its spectrum. Nonlinear group delay dispersion modes are introduced as primitive building blocks for such transformations. Representing spectrotemporal basis functions, these modes and their corresponding time-stretch wavelets have distinct and useful properties that depend on their symmetry. We focus on polynomial basis functions, but also discuss their limitations and alternatives such as spline functions that offer more efficient representation of group delay spectra with localized features. They are used to synthesize complex warped spectrotemporal operations that are reconfigurable and can be implemented in both analog optical and digital (computational) domains. We show how these dispersion-based computational primitives reshape the wideband signal to enable nonuniform sampling, compression, and pattern recognition in real time. Additional applications including coding, signal classification, and enhancement of signal-to-noise ratio during ultrafast analog-to-digital conversion are discussed. Fig. 7. Various methods for realizing optical dispersion. (a) Dispersive optical fiber with internal Raman amplification. (b) chirped fiber Bragg grating (CFBG) used in conjunction with a circulator. (c) CMD. The CMD device offers field reconfigurability of phase and group delay dispersion through tuning of the launch angle of light into the multimode waveguide.

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Giant tunable optical dispersion using chromo-modal excitation of a multimode waveguide

Cited by 54 publications

References 34 publications

Adaptive non-uniform photonic time stretch for blind RF signal detection with compressed time-bandwidth product

Adaptive non-uniform photonic time stretch for blind RF signal detection with compressed time-bandwidth product

Spatial coherence at the output of multimode optical fibers

Tailoring Wideband Signals With a Photonic Hardware Accelerator

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