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An optimized design for a broadband Raman optical amplifier in standard single-mode fiber covering the C and L bands is presented, to be used in combination with wideband optical phase conjugation (OPC) nonlinearity compensation. The use of two Raman pumps and fiber Bragg grating reflectors at different wavelengths for the transmitted (C band) and conjugated (L band) WDM channels is proposed to extend bandwidth beyond the limits imposed by single-wavelength pumping, for a total 10 THz. Optimization of pump and reflector wavelength, as well as pump powers, allows us to achieve low asymmetry across the whole transmission band for optimal nonlinearity compensation. System performance is simulated to estimate OSNR, gain flatness and nonlinear Kerr distortion.

An optimized design for a broadband Raman optical amplifier in standard single-mode fiber covering the C and L bands is presented, to be used in combination with wideband optical phase conjugation (OPC) nonlinearity compensation. The use of two Raman pumps and fiber Bragg grating reflectors at different wavelengths for the transmitted (C band) and conjugated (L band) WDM channels is proposed to extend bandwidth beyond the limits imposed by single-wavelength pumping, for a total 10 THz. Optimization of pump and reflector wavelength, as well as pump powers, allows us to achieve low asymmetry across the whole transmission band for optimal nonlinearity compensation. System performance is simulated to estimate OSNR, gain flatness and nonlinear Kerr distortion.

This chapter documents progress in the extensive area of supercontinuum (SC) generation research devoted to applications in telecommunications, including research into the different mechanisms of spectral broadening and their interplay, SC generation in various media and the most promising SC applications in fibre-based and free-space telecom

In this talk we will review the state of the art on the topic of ultralong passively mode-locked femtosecond pulse fiber oscillators. This new fiber laser architecture relies on the use of polarization-insensitive InN-based semiconductor saturable absorber mirrors (SESAMs) and the careful management of nonlinearities in multi-kilometric fibre rings with Erbium Doped Fiber Amplifier (EDFA)-based amplification. These new sources are capable of supporting the stable generation of soliton-like pulses with durations below 200 fs, overcoming previously assumed limitations to pulse duration in ultralong lasers, and reach ultra-low repetition rates as low as a few tens of kHz with the assistance of Raman amplification. The unique characteristics of this new family of ultrafast fiber oscillators make them suitable for a broad range of potential applications.

Limited polarization control in mode-locked ultralong pulsed ring lasers based on standard telecommunications fiber is shown to reduce pulse duration, noise and chirp and increase pulse peak power with values exceeding 1.5 MW.

Ultrafast-ultralong ring fiber lasers represent a new passively mode-locked laser architecture reliant on the use of Raman-assisted nonlinearity management over cavities extending tens of kilometers and fast, polarization-insensitive saturable absorption. These new sources are capable of supporting the generation of stable pulses shorter than 200 fs with ultra-low repetition rates of a few tens of kHz, overcoming previous limitations to pulse duration and peak power imposed by dispersive effects. The unique characteristics of this new family of ultrafast fiber oscillators makes them suitable for a broad range of applications. In this invited talk we will review some of the latest advances on the topic, focusing on the optimal design and implementation of such lasers.

A system and method for generating ultra-short pulses intended to be inserted into a ring laser with a regulator of a pulsed signal of a certain intensity, the system includes an optical attenuator that allows the intensity of the pulsed signal to be adjusted at the input of an optical guide section, and a distributed amplification device inserted in the optical guide that make it possible to manage the power of the signal therein, so that it propagates as solitons or as self-similar pulses without suffering unwanted distortions despite the increase in the length of the laser cavity, increasing the power of the pulsed signal and making it possible to exceed the usual power limits of this type of laser.

We experimentally explore the relation between spectral linewidth and RIN transfer in half-open cavity random distributed feedback Raman lasers, demonstrating for the first time the possibility of adjusting the pump-to-signal RIN transfer intensity and cut-off frequency by using spectral filtering in the reflector section. We apply this approach to a 50-km laser system, operating in the C-Band, reliant on a standard single-mode fiber. We obtained a minimum bandwidth of 13 pm, which translates into a visible RIN cut-off at 800 MHz.

In this paper, we review different designs of distributed Raman amplifiers which have been proposed to minimize the signal power profile asymmetry in mid-link optical phase conjugation systems. We demonstrate how the symmetrical signal power profiles along the fiber can be achieved using various distributed Raman amplification techniques in the single-span and more realistic multi-span circumstances. In addition, we show the theoretically predicted results of the Kerr nonlinear product reduction with different Raman techniques in mid-link optical phase conjugator systems, and then in-line/long-haul transmission performance using numerical simulations.

[ES] Sistema (1) y procedimiento de generación de pulsos ultracortos destinado a insertarse en un láser (10) de anillo con un regulador (7) de una señal pulsada de una cierta intensidad, comprendiendo el sistema (1) un atenuador óptico (2) que permite ajustar la intensidad de la señal pulsada a la entrada de un tramo de guía óptica (3), y un dispositivo de amplificación distribuida insertado en la guía óptica (3) que permiten gestionar la potencia de la señal en esta, de manera que se propague como solitones o como pulsos autosimilares sin sufrir distorsiones indeseadas a pesar del incremento de longitud de la cavidad del láser, aumentando la potencia de la señal pulsada y permitiendo superar los límites de potencia habituales de este tipo de láser (10)., [EN] System (1) and procedure for generating ultrashort pulses intended to be inserted into a ring laser (10) with a regulator (7) of a pulsed signal of a certain intensity, the system (1) comprising an optical attenuator (2) that allows adjusting the intensity of the pulsed signal at the input of an optical guide section (3), and a distributed amplification device inserted in the optical guide (3) that allows managing the signal power in it, so that propagate as solitons or as self-similar pulses without suffering unwanted distortions despite the increase in the length of the laser cavity, increasing the power of the pulsed signal and allowing to exceed the usual power limits of this type of laser (10).

Localized surface plasmons (LSP) excited by optical fields have many potential applications resulting from their ability in detecting ultra-small, ambient refractive index change. Current methods using surface nano-patterning by means of lithography have given rise to LSP of limited propagation and interaction lengths, meaning that practical applications remain challenging. This article describes a new all-optical method of generating LSP by means of a carefully fabricated low-dimensional nano-structured material using a direct-write photochemical lithography. It is shown that the resulting array of localized SPs combine or “Conjoin” to have an unprecedented large interaction length, via coupled evanescent fields, giving rise to superior spectral sensitivities; several orders of magnitude better than those quoted elsewhere and reaching 6 × 103 nm RIU−1 in the aqueous regime and 104 nm RIU−1 in the gaseous regime. Numerical modeling is performed that shows this design of plasmonic platform is capable of producing sensitivities of 105–106 nm RIU−1. It is believed the results achieved in this investigation show that a unique conjoint SP operational mode will significantly impact areas of interest, such as single molecular dynamics, drug delivery systems, etc.

[EN] The invention relates to a system (1) and method for generating ultra-short pulses intended to be inserted into a ring laser (10) with a regulator (7) of a pulsed signal of a certain intensity, the system (1) comprising an optical attenuator (2) that allows the intensity of the pulsed signal to be adjusted at the input of an optical guide section (3), and a distributed amplification device inserted in the optical guide (3) that make it possible to manage the power of the signal therein, so that it propagates as solitons or as self-similar pulses without suffering unwanted distortions despite the increase in the length of the laser cavity, increasing the power of the pulsed signal and making it possible to exceed the usual power limits of this type of laser (10), {ES] Sistema (1) y procedimiento de generación de pulsos ultracortos destinado a insertarse en un láser (10) de anillo con un regulador (7) de una señal pulsada de una cierta intensidad, comprendiendo el sistema (1) un atenuador óptico (2) que permite ajustar la intensidad de la señal pulsada a la entrada de un tramo de guía óptica (3), y un dispositivo de amplificación distribuida insertado en la guía óptica (3) que permiten gestionar la potencia de la señal en esta, de manera que se propague como solitones o como pulsos autosimilares sin sufrir distorsiones indeseadas a pesar del incremento de longitud de la cavidad del láser, aumentando la potencia de la señal pulsada y permitiendo superar los límites de potencia habituales de este tipo de láser (10), [FR] La présente invention concerne un système (1) de génération d'impulsions ultracourtes destiné à être inséré dans un laser (10) en anneau avec un régulateur (7) d'un signal pulsé à une certaine intensité, le système (1) comprenant un atténuateur optique (2) qui permet d'ajuster l'intensité du signal pulsé à l'entrée d'un segment de guidage optique (3) et un dispositif d'amplification distribuée répartie inséré dans le guide optique (3) qui permettent de gérer la puissance du signal dans ce dernier, de manière à se propager comme des solitons ou comme des impulsions autosimilaires sans connaître de distorsions indésirables malgré l'augmentation de la longueur de la cavité du laser, qui accroit la puissance du signal et permet de dépasser les limites de puissance habituelles de ce type de laser (10)

In distributed optical fibre sensors, the measurement range is typically limited to a few tens of kilometers due to the fibre attenuation and the input pump power limits imposed by the emergence of nonlinear effects. To overcome these problems, distributed amplification schemes have been investigated, generally employing continuous-wave pumping schemes. In this article, we propose the use of Raman amplification with an engineered intensity modulation. We show that this kind of assistance may provide, in principle, a close to perfect loss compensation along the fibre length. To find the optimal modulation profile, an analytical model is presented, and numerically, its performance is analyzed. Using a close to optimal pump modulation profile, we experimentally demonstrate a flat optical trace along 50 km of fibre with a minimal SNR penalty along the length. The result is favorably compared with the continuous-wave pumping case injecting the same average power. Thanks to this new approach, the sensitivity in the worst point is considerably better and the ASD noise floor is also reduced.

We present, for the first time, an experimental demonstration of RIN noise transfer dampening at low frequencies in random distributed feedback ultralong Raman fibre lasers based on conventional telecommunication fibres. Furthermore, we present a thorough theoretical description of the phenomenon and demonstrate how our model can be used to predict the observed behaviour, identifying the general requirements for system improvement through RIN transfer reduction.

We present a theoretical and experimental investigation of unrepeatered transmission over standard single-mode fiber (SMF-28) using several schemes of distributed Raman amplification, including first, second, and dual order. In order to further extend the transmission distance, we utilize advanced bidirectional higher-order ultra-long Raman fiber laser-based amplification, where we use fiber Bragg gratings (FBGs) to reflect Stokes-shifted light from the secondary pumps. Our work demonstrates the possibility of transmission up to 240-km span length with a total span loss of 52.7 dB. Here, we use a 28-Gbaud signal using a 64-quadrature amplitude modulation (QAM) modulation format. Our results highlight the contribution of nonlinear compensation using digital back propagation in a digital signal processor (DSP) code at the receiver.

We present a plasmonic biosensor capable of detecting the presence of bisphenol A in ultralow concentrations, yielding a wavelength shift of 0.15±0.01 nm in response to a solution of 1 fM concentration with limit of detection of 330±70 aM. The biosensing device consists of an array of gold nano-antennae with a total length of 2.3cm that generate coupled localised surface plasmons (cLSPs) and is covalently modified with an aptamer specific for bisphenol A recognition. The array of nanoantennae is fabricated on a lapped section of standard telecommunication optical fibre, allowing for potential multiplexing and its use in remote sensing applications. These results have been achieved without the use of enhancement techniques and therefore the approach allows the direct detection of bisphenol A, a low molecular weight (228 Da) target usually detectable only by indirect detection strategies. Its detection at such levels is a significant step forward in measuring small molecules at ultralow concentrations. Furthermore, this new sensing platform paves the way for the development of portable systems for in-situ agricultural measurements capable of retrieving data on a substance of very high concern at ultra-low concentrations.

We experimentally demonstrate fundamental mode-locked fibre lasing at 1.56¿m in a 2.37 km ring cavity with InN SESAM, with peak powers over 1MW, over 200 nJ pulse energy and pulse durations below 250 fs, Munich ICM, Germany, 23 - 27 June 2019

We report the experimental observation of anomalous RIN transfer function in ultralong random distributedfeedback fiber lasers, confirming theoretical predictions and opening up the possibility of low-frequency RIN reduction via laser design.

We present a plasmonic biosensor capable of detecting the presence of bisphenol A in ultra-low concentrations, yielding a wavelength shift of 0.15 ± 0.01 nm in response to a solution of 1 fM concentration with limit of detection of 330 ± 70 aM The biosensing device consists of an array of gold nano-antennae with a total length of 2.3 cm that generate coupled localised surface plasmons (cLSPs) and is covalently modified with an aptamer specific for bisphenol A recognition. The array of nano-antennae is fabricated on a lapped section of standard telecommunication optical fibre, allowing for potential multiplexing and its use in remote sensing applications. These results have been achieved without the use of enhancement techniques and therefore the approach allows the direct detection of bisphenol A, a low molecular weight (228 Da) target usually detectable only by indirect detection strategies. Its detection at such levels is a significant step forward in measuring small molecules at ultra-low concentrations. Furthermore, this new sensing platform paves the way for the development of portable systems for in-situ agricultural measurements capable of retrieving data on a substance of very high concern at ultra-low concentrations.

We present an experimental demonstration of polarization-independent performance in a forward and backward-pumped 2nd-order ultralong cavity Raman laser amplifiers with highly polarized pumps. Our findings show that the depolarization of the Stokes component due to gain saturation leads to polarization-insensitive performance in terms of output gain and relative intensity noise in the signal. These results pave the way for the use of individual highly polarized low-RIN semiconductor laser diodes in Ramanamplified optical communications.

We demonstrate a low noise bidirectional broadband distributed Raman pumping scheme combining dual order co-propagated pumps without increasing the signal RIN level. The noise performance improvement is compared experimentally and numerically with conventional counter-pumping only and bidirectional pumping with only a 2nd order co-pump for a 70nm bandwidth and 61.5km distributed Raman amplifier. The proposed broadband pumping scheme shows 1.2dB maximum noise figure improvement and extends the long-haul transmission reach up to 6150km with a Q-factor improvement of ~0.7dB compared with counter-pumping only scheme.

The interplay of such cornerstones of modern nonlinear fiber optics as a nonlinearity, stochasticity and polarization leads to variety of the noise induced instabilities including polarization attraction and escape phenomena harnessing of which is a key to unlocking the fiber optic systems specifications required in high resolution spectroscopy, metrology, biomedicine and telecommunications. Here, by using direct stochastic modeling, the mapping of interplay of the Raman scattering-based nonlinearity, the random birefringence of a fiber, and the pump-to-signal intensity noise transfer has been done in terms of the fiber Raman amplifier parameters, namely polarization mode dispersion, the relative intensity noise of the pump laser, fiber length, and the signal power. The obtained results reveal conditions for emergence of the random birefringence-induced resonance-like enhancement of the gain fluctuations (stochastic anti-resonance) accompanied by pulse broadening and rare events in the form of low power output signals having probability heavily deviated from the Gaussian distribution.

Unrepeatered transmission over SMF-28 fibre is investigated using Raman based amplification. Experiments and simulations demonstrate a transmission up to 200 km (41 dB) span length using 28Gbaud 64 QAM modulation employing digital back propagation in DSP.