Add/Drop Mode-Division Multiplexer Based on a Mach–Zehnder Interferometer and Periodic Waveguides.

https://v2.sherpa.ac.uk/id/publication/3538Mode-division multiplexing (MDM) is currently under study due to its potential to further increase data rates in optical communication circuits. In this paper, we propose an add/drop MDM for the first- and second-order modes that cover the whole C-Band (1.53–1.57 m). The device is based on a Mach–Zehnder interferometer, including periodic waveguides in the arms. Mode selectivity is provided by means of the periodic waveguides, which are designed to allow the propagation of the second mode and to reflect the first mode. The proposed device exhibits less than 1 dB insertion loss and more than 30 dB extinction ratio in the whole C-Band. Furthermore, it presents wide fabrication tolerances

Modeling amplified arbitrary filtered heterodyne microwave photonic links

We report an end-to-end analytic model for the computation of the figures of nerit (FOMs) of arbitrarily filtered and amplified heterodyne coherent microwave photonics (MWP) links. It is useful for evaluating the performance of complex systems where the final stage is employed for up/down-converting the radio frequency (RF) signal. We apply the model to a specific case of complex system representing the front-haul segment in a 5G link between the central office and the base station. The model can be however applied to a wider range of cases combining fiber and photonic chip elements and thus is expected to provide a useful and fast tool to analyze them in the design stage.Huawei Technologies (YBN202006512); European Research Council (ADG-2016 UMWP-Chip); Generalitat Valenciana (PROMETEO 2021/015)

Linearization of a Dual-Parallel Mach-Zehnder Modulator Using Optical Carrier Band Processing

The linearization of a microwave photonic link based on a dual-parallel Mach-Zehnder modulator is theoretically de- scribed and experimentally demonstrated. Up to four different radio frequency tones are considered in the study, which allow us to provide a complete mathematical description of all third-order distortion terms that arise at the photodetector. Simulations show that a complete linearization is obtained by properly tuning the DC bias voltages and processing the optical carrier band. As a result, a suppression of 17 dB is experimentally obtained for the third-order distortion terms, as well as a SDFR improvement of 3 dB. The pro- posed linearization method enables the simultaneous modulation of four different signals without the need of additional radio frequency components, which is desirable to its implementation in integrated optics and makes it suitable for several applications in microwave photonics.This work was supported by Huawei under Contract YBN2020095120-SOW3

Integrated Microwave Photonics Coherent Processor for Massive-MIMO Systems in Wireless Communications

Massive-MIMO systems can achieve high capacities and data rates by increasing the number of operational antennas in the base station. As more antenna elements are introduced, the complexity of the signal processing operations increases accordingly and current electronic processors struggle to reach those requirements. To overcome these hurdles, we propose a novel theory to process the RF signals in the optical domain. We experimentally demonstrate the capabilities of theory using a non-integrated Dual Parallel Modulator as a 2×2 optical matrix multiplier, recovering satisfactorily previously mixed RF signals modulated following the standards in 5G communications. Finally, we propose an integrated photonic architecture based on a core of Mach Zehnder Interferometers to physically process the information. Together with the optical core, we proposed the integration of RF modulators, microwave photonic filters and high-speed photodetectors. We present simulations on the expected performance of the circuit and analyze the impact of fabrication errors.This work was supported by the UPV-Huawei Wireless Joint Innovation Center Agreement under Project YBN202009512

Frequency-tuning dual-comb spectroscopy using silicon Mach-Zehnder modulators.

Dual-comb spectroscopy using a silicon Mach-Zehnder modulator is reported for the first time. First, the properties of frequency combs generated by silicon modulators are assessed in terms of tunability, coherence, and number of lines. Then, taking advantage of the frequency agility of electro-optical frequency combs, a new technique for fine resolution absorption spectroscopy is proposed, named frequency-tuning dual-comb spectroscopy, which combines dual-comb spectroscopy and frequency spacing tunability to measure optical spectra with detection at a unique RF frequency. As a proof of concept, a 24 GHz optical bandwidth is scanned with a 1 GHz resolution.Agence Nationale de la Recherche (ANR-17-CE09-0041, ANR-18-CE39-0009)

Frequency-tuning dual-comb spectroscopy using silicon Mach-Zehnder modulators

[EN] Dual-comb spectroscopy using a silicon Mach-Zehnder modulator is reported for the first time. First, the properties of frequency combs generated by silicon modulators are assessed in terms of tunability, coherence, and number of lines. Then, taking advantage of the frequency agility of electro-optical frequency combs, a new technique for fine resolution absorption spectroscopy is proposed, named frequency-tuning dual-comb spectroscopy, which combines dual-comb spectroscopy and frequency spacing tunability to measure optical spectra with detection at a unique RF frequency. As a proof of concept, a 24 GHz optical bandwidth is scanned with a 1 GHz resolution.Agence Nationale de la Recherche (ANR-17-CE09-0041, ANR-18-CE39-0009).Deniel, L.; Weckenmann, E.; Pérez-Galacho, D.; Alonso-Ramos, C.; Boeuf, F.; Vivien, L.; Marris-Morini, D. (2020). Frequency-tuning dual-comb spectroscopy using silicon Mach-Zehnder modulators. Optics Express. 28(8):10888-10898. https://doi.org/10.1364/OE.390041S108881089828

Optical pump-rejection filter based on silicon sub-wavelength engineered photonic structures

The high index contrast of the silicon-on-insulator (SOI) platform allows the realization of ultra-compact photonic circuits. However, this high contrast hinders the implementation of narrow-band Bragg filters. These typically require corrugations widths of a few nanometers or double-etch geometries, hampering device fabrication. Here we report, for the first time, on the realization of SOI Bragg filters based on sub-wavelength index engineering in a differential corrugation width configuration. The proposed double periodicity structure allows narrow-band rejection with a single etch step and relaxed width constraints. Based on this concept, we experimentally demonstrate a single-etch, $\mathbf{220\,nm}$ thick, Si Bragg filter featuring a corrugation width of $\mathbf{150\,nm}$, a rejection bandwidth of $\mathbf{1.1\,nm}$ and an extinction ratio exceeding $\mathbf{40\,dB}$. This represents a ten-fold width increase compared to conventional single-periodicity, single-etch counterparts with similar bandwidths

Simplified modeling and optimization of silicon modulators based on free-carrier plasma dispersion effect

n this paper, a simplified model of silicon phase modulators is presented that enables favorable accuracy together with a substantial reduction in computational effort and without the requirement of semiconductor TCAD device simulation software. This permits fast optimization of the different parameters of a modulator. The model was successfully implemented in Phoenix Optodesigner optical software allowing the optimization of silicon phase shifters for different applications. Moreover, this model presents a great potential for the simulation of modulators based on PN interdigitated junctions, which normally require complex and time consuming 3D simulations. Simulation time was reduced by a factor of 6 for the lateral PN junction based modulator, and two orders of magnitude reduction was obtained for interdigitated PN junctions based modulators.French National Research Agency (ANR), project Ultimate (ANR-11-INFR-0015); European Commission, project Plat4m (FP7-2012-318178)

Silicon subwavelength modal Bragg grating filters with narrow bandwidth and high optical rejection

[EN] Waveguide Bragg grating filters with narrow bandwidths and high optical rejections are key functions for several advanced silicon photonics circuits. Here, we propose and demonstrate a new, to the best of our knowledge, Bragg grating geometry that provides a narrowband and high rejection response. It combines the advantages of subwavelength and modal engineering. As a proof-of-concept demonstration, we implement the proposed Bragg filters in 220-nm-thick Si technology with a single etch step. We experimentally show flexible control of the filter selectivity, with measured null-to-null bandwidths below 2 nm, and strength of 60 dB rejection with a null-to-null bandwidth of 1.8 nm.Agence Nationale de la Recherche (ANR-MIRSPEC-17-CE09-0041, ANR-SITQOM-15-CE24-0005); European Research Council (ERC POPSTAR 647342).Oser, D.; Pérez-Galacho, D.; Le Roux, X.; Tanzilli, S.; Vivien, L.; Labonte, L.; Cassan, E.... (2020). 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