M.E. Marhic's research while affiliated with Swansea University and other places

... The optical receiver consist of a telescopic system having a primary and secondary mirror, a block of beam splitter, a spherical aberration from chromatic components and diaphragm placed along an optical axis of the optical receiver. The chromatic component is used to demultiplex the wavelength channels of the input optical beam of the receiver in such a way that channels are focused at different focal planes on the optical axis of the receivers [6,13]. ...

... Optical gain clamping (OGC) has been shown to offer a number of attractive features for improving the performance of EDFAs [6] and Raman amplifiers [7] in dynamic wavelength division-multiplexed (WDM) networks, but is relatively unexplored in FOPAs. Previously, a gain-clamped FOPA (GC-FOPA) was shown theoretically to improve performance for optical packet transmission in FOPAs [8, 9] and gain clamping for a single signal channel was experimentally investigated in [10]. Here, we experimentally investigate the practical viability of using OGC in a dynamic network environment and find only moderate practical benefit in terms in reducing the impact of bit-level XGS but may provide application for static gain control schemes. ...

... Fiber dispersion-induced power fading can be eliminated by using an OSSB signal [21]. Several techniques for implementing an OSSB signal have already been proposed, such as using optical filtering to remove one of the first-order sidebands of DSB signals [22][23][24], dual-drive Mach-Zehnder modulator (DDMZM) [25,26], dual-parallel MZM (DPMZM) [27][28][29], hybrid structure composed of a cascade of an amplitude modulator (AM) and a PM [30,31] and based on a polarization modulator (PolM) [32]. ...

... Note that the fast response time of the FWM process, which makes FOPAs useful for many important applications, also helps transferring noise from the pumps to the signal efficiently. Several groups have suggested that the noise associated with the pumps is one of the dominant sources of signal SNR degradation [8], [77]- [79], [88]- [91]. Section 5.2 extends the earlier works to the case of dual-pump FOPAs and shows that the group-velocity difference between the signal and pumps has to be taken into account to determine the noise transfer correctly [92]. ...

... In order to address this crosstalk problem, we recently proposed using a hybrid amplifier formed by a fiber OPA with moderate gain, followed by a (non-fiber-OPA) PIA, as a novel and effective means for reducing the FWM crosstalk [16]. This is based on the fact that FWM between signals occurs primarily where signals are the strongest, i.e. near the amplifier output; hence using an amplifier less prone to FWM as a booster will reduce FWM crosstalk (for the same overall gain). ...

... Yam et.al used a pair of band-pass wavelength division multiplexers (WDMs) at the input and output of the RFA. The pass and reflected bands of the WDMS are carefully selected so that the signals and lasing output do not reside in the same band [3]. Bolognini et al. achieved gain-clamping through an optical feedback made of a combination of circulator at the input and a coupler at the output, which generates a counter-propagating laser by filtering a small ASE fraction; a variable optical attenuator (VOA) is used to clamp the gain at different values depending on the span loss which must be compensated by the RFA gain [4]. ...

... Cascade systems are widely used in various electrical and electronics engineering domains such as telecommunications and signal processing [1][2][3][4][5][6][7], circuits [8][9][10][11][12][13][14][15][16], networks and systems [17][18][19][20], solid-state devices [21][22][23][24][25][26][27][28][29], and so on. To extract the actual signal component at the output of these systems, it is critical to calculate its total noise factor (F T ). ...

... where V J 1 J 2 (κ j , κ j ; t, t 0 ) = V J 1 J 2 ;j,j (t, t 0 )/∆κ, (334) W J 1 J 2 (κ j , κ j ; t, t 0 ) = W J 1 J 2 ;j,j (t, t 0 )/∆κ. We note that similar input-output relations were also derived in [72,[97][98][99], albeit with different labels. ...

... Although the FOPAs have their inherent advantage of wide gain bandwidth and are flexible in choosing the gain region via varying pump wavelengths, they offer a low gain, particularly if the number of channels is large. To increase the gain, hybrid FOPAs have been proposed [5][6][7]. A hybrid of FOPA with an erbium-doped fibre amplifier (EDFA) reduces the FWM crosstalk and leads to good gains [7]. ...

... In Ref. [16], a CW single-longitude-mode FOPO was reported, including a saturable-absorber-based Sagnac loop and an erbium-doped fiber. The filters used in the reported CW FOPOs typically have, however, high insertion losses-in the range of 3-5 dB [14][15][16][17][18][19]. These lead to high cavity losses and limitations to further improvement of FOPO performance. ...