Commercial Erbium-doped Fiber Amplifiers Research Articles

Broadband optical nonreciprocity by emulation of nonlinear non-Hermitian time-asymmetric loop

Broadband and power-stable optical nonreciprocity is highly desirable for practical implementation of optical isolation of coherent sources and receivers in high-speed data-processing systems. Here, we experimentally demonstrate a 2 × 2 waveguide-coupler system that produces broadband optical nonreciprocity based on simple emulation of nonlinear non-Hermitian time-asymmetric loop. The coupler system consists of five lumped optical components including two linear attenuators and two saturable amplifiers. Under moderate operation conditions which are routinely obtainable with commercial erbium-doped fiber amplifiers, we obtain 20 dB isolation ratio persisting over the entire gain bandwidth of the amplifier and over a wide incident-intensity range from 0.1 mW to 10 kW. The isolation ratio can be enhanced up to 70 dB with the forward transmission efficiency adjustable at any desired stable point by tuning amplifier’s internal dissipation in principle. Therefore, our result strongly encourages further experimental development of broadband on-chip optical isolators which have been elusive so far.

Fibre optic parametric amplifier for high capacity burst-mode access networks.

We compare performance of a polarization insensitive fiber optic parametric amplifier (PI-FOPA), a commercial erbium doped fiber amplifier (EDFA) and a discrete Raman amplifier (DRA) in a 50 km long-reach optical access network transmitting bursts of 10 Gbps signal with traffic density ranged from 5% to 97%. We demonstrate that for the same power budget the PI-FOPA allows for transmission of bursty traffic with density up to 97% while DRA and EDFA are limited to 30% and 15%, respectively. Alternatively, we demonstrate PI-FOPA to allow for 3 dB and 5 dB higher power budget than the DRA and EDFA, respectively, for the worst case scenario of 75% traffic density.

Enhancing Lightpath QoT Computation With Machine Learning in Partially Disaggregated Optical Networks

Increasing traffic demands are causing network operators to adopt disaggregated and open networking solutions to better exploit optical transmission capacity, and consequently enable a software-defined networking (SDN) approach to control and management that encompasses the WDM data transport layer. In these frameworks, a quality of transmission estimator (QoT-E) that gives the generalized signal-to-noise ratio (GSNR) is commonly used to compute the feasibility of transparent lightpaths (LP)s, taking into account the amplified spontaneous emission (ASE) noise and the nonlinear interference (NLI). In general, the ASE noise is the main contributor to the GSNR and is also the most challenging noise component to evaluate in a scenario with varying spectral loads, due to fluctuations in the optical amplifier responses. In this work, we propose a machine learning (ML) algorithm that is trained using different ASE-shaped spectral loads in order to predict the OSNR component of the GSNR; this methodology is subsequently used in combination with a QoT-E in the lightpath computation engine (L-PCE). We present an experiment on a point-to-point optical line system (OLS), including 9 commercial erbium-doped fiber amplifiers (EDFA)s used as black-boxes, each with variable gain and tilt values, and 8 fibers that are characterized by distinct physical parameters. Within this experiment, we receive the signal at the end of the OLS, measuring the bit-error-rate (BER) and the power spectrum, over 2520 different spectral loads. From this dataset, we extract the expected GSNRs and their linear and nonlinear components. Through joint application of a ML algorithm and the open-source GNPy library, we obtain a complete QoT-E, demonstrating that a reliable and accurate LP feasibility predictor may be implemented.

Experimental comparison of fiber optic parametric, Raman and erbium amplifiers for burst traffic for extended reach PONs.

We experimentally compare the performance of a polarization-independent fiber optic parametric amplifier (FOPA), a discrete Raman amplifier and a commercial erbium doped fiber amplifier (EDFA) for burst traffic amplification in extended reach passive optical networks (PON). We demonstrate that EDFA and Raman amplifiers suffer from severe transient effects, causing penalty on receiver sensitivity >5 dB for traffic bursts of 10 Gbps on-off keying signal shorter than 10 µs. On the other hand, we demonstrate that FOPA does not introduce a penalty on receiver sensitivity when amplifying signal bursts as short as 5 µs as compared to a non-burst signal. Therefore, FOPA used as a drop-in replacement for an EDFA or Raman amplifier allows us to improve receiver sensitivity by >3 dB for short signal bursts. We conclude that FOPA allows substantially increased power budget for an extended reach PON transmitting variable duration bursts. In addition, we identify the maximum burst duration tolerated by each examined amplifier.

Multi-Band Direct-Detection Transmission Over an Ultrawide Bandwidth Hollow-Core NANF

In this article, we report high-speed multi-band direct-detection (DD) transmission over a hollow-core nested antiresonant nodeless fiber (NANF). Thanks to the ultrawide bandwidth of the NANF, we demonstrate dual-band transmission across the O- and C-bands over a ∼1-km length of a hollow-core fiber for the first time. Eight wavelength-division multiplexed (WDM) channels were transmitted using 100-Gb/s/λ Nyquist 4-ary pulse-amplitude modulation (PAM4) signals, which to the best of our knowledge, is the highest aggregate capacity ever transmitted in a DD hollow-core fiber-based transmission system. Optical pre-amplification was adopted for signal reception in both bands, achieved using an in-house built bismuth-doped optical fibre amplifier (BDFA) and a commercial erbium-doped fiber amplifier (EDFA) in the O- and C-band, respectively. We further demonstrate beyond 100-Gb/s/λ adaptively-loaded discrete multitone (DMT) transmission over the S+C+L-bands using the same NANF, without the use of optical amplification. Our experiments show that apart from fiber loss, the use of the NANF did not introduce any additional transmission penalties. The demonstrated results validate the ultrawide bandwidth and excellent modal purity of the fabricated NANF, which allow beyond 100-Gb/s/λ penalty-free transmission over multiple bands, highlighting the potential of this fiber technology for high-speed short- to intermediate-reach applications.

Efficient frequency doubling at 776 nm in a ring cavity

We report efficient frequency doubling (FD) at 776nm using periodically poled LiNbO3 (PPLN) in a ring cavity pumped by a commercial erbium-doped fiber amplifier (EDFA) operating at 1552nm. Two sets of input couplers are used that have been optimized to operate in the low pump and high pump regimes. The maximum conversion efficiencies measured for these couplers are 65.8% (transmittance T=4.5%) and 65.9% (T=9.1%). The internal conversion efficiencies are 85.0% and 88.2%, respectively, after the mode-matching efficiency and filtering transmittance have been taken into account. The maximum output powers obtained for the two couplers are 333mW and 602mW at pump powers of 535mW and 999mW, respectively. Coupling efficiency of more than 80% to single mode fibers indicates the high beam quality of the FD laser. This FD laser will be useful for quantum optics experiments in the telecommunications band and atomic physics experiments.

9.6Tb/s CP-QPSK Transmission Over 6500 km of NZ-DSF With Commercial Hybrid Amplifiers

We experimentally demonstrate, for the first time to the best of our knowledge, an ultralong-haul dense wavelength division multiplexed transmission of $96 \,\, \times \,\, 100$ Gb/s coherent polarization multiplexed quadrature phase-shifted keying transponders over ITU-T G.655 nonzero dispersion-shifted large effective area fibers (NZ-DSF) with an effective core area of 72 $\mu \text{m}^{2}$ , employing both commercial erbium-doped fiber amplifiers (EDFA) and hybrid EDFA + Raman amplification systems. Using the state-of-the-art digital pulse shaping and digital preemphasis algorithms, we report $\sim 1.5$ dB back-to-back optical signal-to-noise ratio penalty at pre forward error correction (FEC) bit error rate (BER) threshold ( $3.8\times 10^{-2}$ ), with respect to theoretical performance. In particular, we demonstrate $\sim 6500$ km transmission across the entire C-band, at pre-FEC BER of $3.8\times 10^{-2}$ , employing EDFA + backward Raman amplification—where the central channel (1552.2nm) had sufficient margin to enable transmission of up to $\sim 8000$ km. Furthermore, we report that hybrid amplification enables up to $\sim 60$ % improvement in maximum transmission reach, compared to EDFA based links. To the best of our knowledge, a record capacity-distance product of $\sim 62.4~\textrm {Pb}/\textrm {s}\cdot \textrm {km}$ is achieved for NZ-DSF—an 11-fold increase, compared with the previous literature.

Mode-locked erbium-doped fiber lasers as source for optical sensor networks over C and L bands

The performance of mode-locked erbium-doped fiber lasers in optical sensor networks is analyzed and compared with the results obtained by using commercial erbium-doped fiber amplifiers as source. Passive mode-locked lasers developed are based on nonlinear polarization rotation and they have been built using the same erbium-doped fiber amplifiers. To simulate a real sensor network, a tree structure with four fiber Bragg gratings was built employing 50/50 couplers. The mode-locked laser developed offers a reasonably good behavior at a very wide spectral range (83nm, approximately) over C and L bands. The signal to noise ratio and the peak power are greatly improved with regard to the values obtained employing commercial amplifiers as source.

Broadband Chromium-Doped Fiber Amplifiers for Next-Generation Optical Communication Systems

We report the first experimental breakthrough of a net gain of optical signals in a broadband chromium-doped fiber amplifier (CDFA) for next-generation optical communication systems. Current fiber amplifiers, including commercial erbium-doped fiber amplifier, cover only a relatively small portion of the entire transmission bandwidths (1300-1600 nm) of the low-loss windows of silica fibers. The newly developed CDFAs have opened up the possibility of utilizing the 300-nm entire spectrum of the low-loss fibers to further increase the transmission capacity. In this paper, we present the experimental demonstration of a net gain of 1.2 dB employing gain enhancement technique. With the help of an optical-fiber system examination for the CDFA, a 40-Gb/s error-floor free data transmission was successfully demonstrated by realizing the high-speed transmission of signal with gain through the chromium-doped fibers (CDFs). Further gain improvement in the CDFAs employing few-mode or single-mode CDFs will be presented and discussed.

Experimental comparison of WDM system capacity in conventional and nonzero dispersion shifted fiber

A primary consideration in designing new backbone optical network segments is the total data capacity of each fiber span. We compare the wavelength-division-multiplexed capacity of conventional single-mode fiber (SMF) and nonzero dispersion shifted fiber by measuring performance versus channel spacing in 4/spl times/80 km transmission of five 10 Gb/s channels at the nominal commercial erbium-doped fiber amplifier power specification of 9 dBm/ch. The achievable capacity is found to be more than four times greater in conventional SMF.