Repeater Power Conversion Efficiency in Submarine Optical Communication Systems

Abstract

In power-limited trans-oceanic submarine systems, the electrical-to-optical (E/O) power conversion efficiency determines the amount of optical signal power generated by repeaters, which governs the cable capacity. In contrast to conventional submarine systems, recent single mode fiber spatial division multiplexing (SDM) systems operate at a lower channel power and support a larger number of optical fibers. Moreover, pump sharing technology is used in SDM systems to enhance cable capacity and system reliability, where a group of pump lasers are combined to feed a group of fiber pairs. The repeater E/O power conversion efficiency is directly related with cable capacity, as well as capacity per power and cost per capacity analysis. Therefore, it is important to understand the characteristics of repeater E/O efficiency. We developed a model to analyze the repeater E/O efficiency in submarine SDM systems. Experimental measurement data of pump lasers and numerical simulation results of Erbium doped fiber amplifiers (EDFAs) were used as input information to the model to analyze repeater E/O efficiency in vario us system designs. Based on the E/O efficiency model results, we investigated cable capacity using the Gaussian noise (GN) model. Moreove r, cable capacity per power was calculated and compared based on three different power metrics: (i) electrical supply power, (ii) pump optical power and (iii) EDFA output power. With the ai d of the repeater E/O efficiency model, one can analyze the efficiency of submarine systems using the direct metric of cable capacity per electrical supply power.

Power-efficient undersea SDM systems

“…For this PE definition, the key parameter determining cable capacity for any EDFA output power via the number of fiber pairs (FPs) supported is the E-O conversion efficiency. A previously developed pump farming model [29] was used to estimate the E-O conversion efficiency as a function of the EDFA output power, gain, and available repeater power. Pump farming is employed in SDM submarine systems to enhance power efficiency and system resilience and consists of a pool of pump lasers whose output lightwaves are combined through a coupler network and then divided to pump multiple fiber pair EDFAs.…”

“…We first look at five different ways to measure fiber capacity and the two basic power metrics using EDFA output power and optical pump power, respectively. We will also consider a third power efficiency metric based on an estimate of the total cable capacity allowed with fixed cable electrical power supply and applying a pump farming model [29] to predict overall electrical-to-optical (E-O) conversion efficiency as a function of EDFA output power. We compare the optimal GSNR values predicted for all three power efficiency definitions and show results of the dependence on various parameters such as span loss, link length, and fiber attenuation.…”

Cable Capacity and Cost/Bit Modeling of Submarine MCF Systems With MC-EDFA Alternatives

“…Fiber capacities and thus total cable capacities are calculated using the Gaussian Noise (GN) model [26,27] for coherent transmission in dispersion-unmanaged systems. We use a pump sharing model as described in [28] for SC-EDFAs that estimates overall electrical-to-optical (E-O) conversion efficiency as a function of repeater power, EDFA output power, and span loss. For the MC-EDFAs, we modify the E-O conversion efficiency from the baseline by the relative efficiency penalty incurred by the MC-EDFA configuration (if any) as described shortly.…”

“…Secondly, we analyzed the E-O conversion efficiency of the MC-EDFAs compared to parallel SC-EDFAs and the results of our assessment are summarized in Table II. As detailed in references [28,29], the overall E-O conversion efficiency of submarine repeaters can be calculated as η=η driver •η aging •η pump •η EDF •η GFF , where η driver is the efficiency of the electrical current driver, η aging accounts for the current required to accommodate pump LD aging over a 25-year lifespan, η pump is the E-O conversion efficiency of the pump LD, η EDF is the optical power conversion efficiency (OPCE) of the erbium doped fiber and η GFF is the associated power loss due to the use of a gain flattening filter (GFF). Here, the E-O conversion efficiency of the pump LD and the OPCE of the EDF are the most important differentiating factors that lead to the difference in the overall amplifier efficiency between architectures.…”