In this paper we present results from the study of optical signal amplification using Raman assisted fiber optical parametric amplifier with considerable benefits for S-band telecommunication systems where the use of widely used erbium-doped fiber amplifier is limited. We have created detailed models and performed computer simulations of combined Raman and fiber optical parametric amplification in a 16-channel 40 Gbps/channel wavelength division multiplexed transmission system. Achieved gain bandwidth, as well as transmission system parameters—signal-to-noise ratio and bit-error-ratio—were analyzed by comparing the Raman assisted fiber optical parametric amplifier to the single pump fiber optical parametric amplifier. Results show that the 3 dB gain bandwidth in the case of combined amplification is up to 0.2 THz wider with 1.9 dB difference between the lowest and highest gain.

Cladding-pumped erbium (Er³⁺)/ytterbium (Yb³⁺)-co-doped fiber amplifiers are more advantageous at high output powers. However, this amplification technique also has potential in telecom-related applications. These types of amplifiers have complex properties, especially when considering gain profile and a pump conversion efficiency. Such metrics depend on the doped fiber profile, absorption/emission spectra, and the input signal power. In this context, we design, build and characterize an inhouse prototype of cladding-pumped Er³⁺/Yb³⁺-co-doped fiber amplifier (EYDFA). Our goal is to identify the EYDFA configuration (a co-doped fiber length, pump power, input signal power) suitable for signal amplification in a multichannel fiber-optic transmission system with a dense wavelength allocation across the C-band (1530–1565 nm). Our approach involves experimentally determining the Er³⁺/Yb³⁺-co-doped fiber’s parameters to be used in a simulation setup to decide on an initial EYDFA configuration before moving to a laboratory setup. An experimental EYDFA prototype is tested under different conditions using a 48-channel dense wavelength division multiplexing (DWDM, 100 GHz) system to evaluate the absolute gain and gain uniformity. The obtained results allow the cladding pump amplifier’s suitability for wideband signal amplification to be assessed. The developed prototype provides >21 dB of gain with a 12 dB ripple within 1534–1565 nm. Furthermore, we show that the gain profile can be partially flattened out by using longer EYDF spans. This enhances signal amplification in the upper C-band in exchange for a weaker amplification in the lower C-band, which can be marginally improved with higher pump powers.

In this paper we present computer simulation results of a phase-sensitive fiber optic parametric amplifier (PS-FOPA) in the so-called dual-pump degenerate configuration using highly non-linear fiber (HNLF) with the pump lasers’ frequencies located symmetrically around the signal central frequency with 200 GHz offset. The main purpose of the study was the evaluation of PS-FOPA regeneration performance for differentially encoded binary phase shift keying (DPSK) signals, taking into account pump laser power, signal distortion level, and HNLF chromatic dispersion. A relationship has been established between noisiness of the input signal and optimal power levels providing the lowest output signal bit error ratio. Higher noise levels require higher signal input power to reach the point of gain saturation. Chromatic dispersion coefficient of the HNLF has a substantial impact on the regenerator’s performance. Positive values show a rapid drop-off in performance while negative values can allow greater signal quality improvement at the cost of higher input power.

This paper provides an overview of most recent and promising techniques on how to improve signal regeneration based on FWM process. This includes the mitigation of undesirable effects dispersion has on FWM or using it to our advantage with channel-specific dispersion compensation. Experimental verification of the feasibility of copier-PSA for long-haul in-line amplification is evaluated. It is also shown that effective use of pump polarisation allows the reduction of noise during regeneration of advanced modulation formats and can facilitate multi-channel operation. Some novel phase quantisation techniques are highlighted which provide higher accuracy than conventional methods.