Experimental validation of an extended ABCD model for activelymode-locked fiber lasers

An extended ABCD model for actively mode-locked fiber lasers is presented. This new scheme includes the amplifier model taking into account the power evolution along the cavity fiber. The first experimental validation is reported     

Electrochemical Approach to Copper‐Catalyzed Reversed Atom Transfer Radical Cyclization

Electrochemically mediated atom transfer radical cyclization (eATRC) has been developed as an easy and clean method allowing the synthesis of halogenated cyclic compounds. This method has been successfully applied to the copper‐catalyzed atom transfer radical cyclization of some N‐allyl‐α,α‐dichloroamides in acetonitrile (CH₃CN) using a copper complex with tris(2‐pyridylmethyl)amine (TPMA) with a metal loading of 1%. The catalyst is introduced as [Cu(II)TPMA]²⁺ and is activated and continuously regenerated to its active copper(I) form by reduction at a platinum (Pt) electrode. During the ATRC process a new copper(II) complex, namely, [ClCu(II)TPMA]⁺, whose reduction potential is ca. 0.350 V more negative than that of the starting [Cu(II)TPMA]²⁺, is formed. Therefore, the choice of the applied potential is critical and should be done taking care that all copper(II) species are reduced to copper(I). The compounds undergo very high conversions (79–100%) in a few hours of electrolysis, producing a cyclic γ‐lactam (yield 60–98%) as a mixture of two isomers, with a good cis‐diastereoselectivity [dr (cis/trans)=59/41–83/17]. [Cu(II)PMDETA]²⁺ (PMDETA=N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine), which is much cheaper, albeit less reactive than [Cu(II)TPMA]²⁺, was also investigated but the results were not satisfactory.

     

All-optical regeneration and demultiplexing for 160-gb/s transmission systems using a NOLM-based three-stage scheme

An all-optical pulse regenerator suitable for 160-Gb/s transmission systems, including three stages based on nonlinear optical loop mirrors, is proposed. The idea of splitting the regeneration process in three different steps allows the use of easy and well-known ultrafast subsystems. This approach offers advantages in terms of maximum bit rate of the signals that can be regenerated. The significant signal improvement in terms of noise reduction, pulse reshaping, and jitter suppression introduced by the regenerator is experimentally evaluated. A Q-factor increase from 3.2 to 6.3 was measured for the eye diagram. Since the presented scheme can also be exploited as a regenerating demultiplexer, simultaneous regeneration and demultiplexing functions are implemented for data signals up to 160 Gb/s.     

Broadcasting in colorless WDM-PON using spectrum-sliced wavelength conversion

We propose and experimentally demonstrate a novel wavelength-division-multiplexed passive optical network (WDM-PON) scheme for providing broadcasting service by using an inverted amplified spontaneous emission (ASE) from a semiconductor optical amplifier (SOA). In this scheme, single pump signal is converted into multiple wavelengths signal by spectrum sliced wavelength conversion. We expect it could be very practical and cost-effective solution for broadcasting in WDM-PON due to its simplicity.     

New optical sampler based on TOAD and data postprocessing for subpicosecond pulse resolution

A low-complexity terahertz optical asymmetric demultiplexer-based optical sampler with simple data postprocessing for subpicosecond pulse shape characterization is proposed. Comparisons with commercial instruments demonstrate the accuracy of the implemented scheme reproducing optical pulses with a resolution of few hundreds of femtoseconds. Nevertheless, the proposed technique allows us to go down to femtosecond accuracy, slightly increasing the data postprocessing complexity. A further validation of the proposed optical sampler is numerically provided.     

Efficient and Green Route to γ‐Lactams by Copper‐Catalysed Reversed Atom Transfer Radical Cyclisation of α‐Polychloro‐N‐allylamides,using a Low Load of Metal (0.5 mol%)

The cyclisation of N‐allyl‐N‐substituted‐α‐polychloroamides is efficiently obtained through a copper‐catalysed activators regenerated by electron transfer–atom transfer radical cyclisation process, with a metal load of only 0.5 mol%. The redox catalyst is introduced in its inactive form as copper(II) chloride/[nitrogen ligand] complex, and continuously regenerated to the active copper(I) chloride/[nitrogen ligand] species by ascorbic acid. To preserve the catalyst integrity, the hydrochloric acid, released after each regeneration cycle, has been quenched by carbonate. The choice of the solvent is critical, the best performance being observed in ethyl acetate‐ethanol (3:1).     

Undecylenic acid: A valuable renewable building block on route to Tyromycin A derivatives

A key intermediate for the synthesis of Tyromycin A, a C‐20 tetrachlorodicarboxylic acid, was produced in six steps starting with the dimerization of methyl 10‐undecenoate which was obtained from a renewable resource, e.g. castor oil. The acyloin condensation product was then oxidized, transformed to the diene, followed by ozonization, chlorination and finally oxidation to the corresponding tetrachlorodicarboxylic acid.     

Impact of an Additional All-Optical Decision Element in Band-Limited Receivers for RZ Systems

We investigate both theoretically and experimentally how the use of an all-optical decision element (ODE) in front of a conventional receiver improves, in return-to-zero (RZ) systems, the receiver performance when the signal bandwidth exceeds the bandwidth of the available optoelectronic components. A theoretical analysis of the ODE behavior shows the field of applicability of the investigated solution. The experimental evaluation of the performance improvement in an RZ system is realized using an ODE based on two cascaded nonlinear optical loop mirrors. Benefits in terms of bit error rate for different signal bandwidths and for a different received optical signal-to-noise ratio are presented. Substantial agreement of the experimental results with the theoretical analysis is obtained. The impact of the ODE in the presence of relevant thermal noise at the receiver is also considered. The ODE can extend the use of common band-limited receivers to wide-bandwidth signals and can be an alternative solution to the development of wideband receivers.