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We propose using SDM/TDM translation method to signals amplified by CC-MC-EDFA in a scalable manner to the number of MCF core. We confirmed identical signal quality of the CC-4C-EDFA among 4 cores even if ±0.65dB output optical power fluctuated due to inter-core crosstalk appears.

For C band application, the optical amplification efficiency of cladding pumped multicore EDFA is still problematic as a major part of the pump light is not absorbed in the short doped fiber. In this paper, we study the pump recycling technology. The operation principle is introduced and verified experimentally. Also, fundamental optical amplification performance is characterized. Moreover, feasibility of the application to multicore optical transmission systems is researched.

We show recent technologies for low power consumption multi-core amplifiers. We report advances concerning core pumping, cladding pumping and optimized hybrid pumping technologies for power efficient optical amplification with erbium doped multi-core fiber amplifiers.

We have successfully confirmed the feasibility of real-time optical gain spectrum monitoring of CC-MC-EDFA with the standard deviation within 0.65 dB even if the optical power per core fluctuate due to the inter-core crosstalk.

Optical submarine cables are a crucial infrastructure as they convey 99% of internet traffic between countries and continents. Although, their history is rooted in the middle in the 19th Century with the first transatlantic telegraph cable, the uninterrupted strong growth of current internet traffic has been a prime motivation for the introduction of several disruptive technologies. In this paper, we review technologies used in past and current optical submarine cables, as well as future technological trends to increase their capacity.

We have confirmed 1.5 dB optical gain improvement with a ±0.6 dB dependence among cores by applying the turbo cladding pumping scheme. The turbo scheme does not degrade optical gain and NF, nor their uniformity.

We demonstrate compact and low-loss $8 \times 8$ silicon photonic switch modules, which are applicable to transponder aggregators (TPAs) in colorless, directionless, and contentionless reconfigurable optical add-drop multiplexers. Newly designed silicon optical switch chips incorporating spot size converters with polarization insensitive and wavelength insensitive properties over C/L bands are packaged. The developed module shows about 6-dB average excess optical loss, including optical coupling loss, on all 64 optical paths with low-polarization-dependent loss and low crosstalk. Using these compact optical switch modules, we construct a TPA prototype featuring over 100-port optical switch subsystem densely mounted on one board and confirm its feasibility.

We used paired prototypes of spatial pump combiner and splitter to improve the pump recycling ratio of turbo cladding pumped MC-EDFA from 12% to 42%. This enables a potential 1.2dB improvement of the optical gain.

We report advances in low power consumption multi-core amplifiers. We namely show recent advances concerning core pumping, cladding pumping and hybrid pumping technologies for power efficient optical amplification with erbium doped multi-core fiber amplifiers.

Configurations of cladding pumped MC-EDFA with pump recycling have been researched to improve optical amplification efficiency. The difference between the four researched configurations is the pump injection and re-injection method. The optical amplification performance was compared experimentally by evaluating the optical gain, noise figure, and the maximum output signal power. The results show the spatial injection and the fiber re-injection with spatial splitting configuration improved the pump recycling efficiency the most, and the configuration offered an additional 3.5 dB of optical gain and boosted the maximum output signal power by 4.0 dB compared to the standard cladding pumping without pump recycling. The improvement in the optical gain due to the pump recycling was constant at 1.0 dB in the fixed experimental set-up even if the input optical signal power was changed. The effect of the spatial intensity distribution widening due to the fiber pump combiner is considered to be effective in improving the pump recycling efficiency. An additional 0.2 dB improvement (1.2 dB in total) in the optical gain was achieved by modifying the free-space lens optics design of the spatial pump splitter.

We report advances in power-efficient SDM transmission technologies. We emphasize on the system design and the benefits of SDM technologies. We show progresses of power-efficient multicore amplifiers.

We have confirmed 110 km MCF stable real-time transmission of PM-16QAM signal amplified with novel turbo cladding pumping scheme. Optical gain was improved by 2 dB as we recycled residual $0.98\ \mu m$ pump, enabling 32% reduction of power consumption.

We clarify the optimal pumping schemes for SDM/WDM channel allocation with a 7-core hybrid MC-EDFA. We report up to 20% of power consumption at maximum capacity. We estimate the benefits from improvement of cladding pumping.

Silicon photonic switches are attractive for extensible optical switch systems required for optical networks in telecom areas and datacenters. We show our low-loss silicon photonic switch modules and their application to CDC-ROADMs using multiple modules.

We show 39 % reduction of amplification power consumption with cladding pump MC-EDFA using 16-core spectral superchannels over SDM NSFNET16 topology. Impairment aware least wavelength bandwidth routing algorithm further reduces the power consumption by 45%.

We transmit 256Gb/s PM-16QAM signal through 385km with 7-core MCF, passing 7 times a MC-EDFA with common cladding and variable shared core pumping. The MC-EDFA enables 23% reduction of power consumption while received Q value varied within ±0.17dB.

As a promising device platform technology for optical switches, silicon photonics is recently attracting much attention. In this paper, we demonstrate compact 8×8 silicon photonic switch modules with low loss, low polarization sensitivity, and low cross-talk properties. These optical switch modules are intended for applying to ROADMs in telecom optical networks, but port count extensibility using multiple compact modules and faster switching based on thermo-optical effect of silicon are useful also for datacenter applications.