The National Institute of Information and Communications Technology (NICT, President: Hideyuki Tokuda, Ph.D.) and Furukawa Electric Co., Ltd. (Furukawa Electric, President: Keiichi Kobayashi) jointly report a record SDM transmission experiment using multi-core fiber amplifier. Furukawa Electric developed a 19-core Erbium-doped-fiber amplifier utilizing cladding-pumping technology in order to share electrical power between the large number of spatial channels. The amplifier was then integrated into NICT’s state of the art transmission test bed of for a record transmission demonstration. Fully decoded optical data transmission of 715 Tb/s was achieved over a distance of 2,009 km using coded polarization division multiplexed (PDM) -16 quadrature-amplitude modulation (QAM) of 345 carriers over the C and L band in a re-circulating transmission loop.

Previously, short-distance, high-capacity transmission in high-core count EDFAs and long-distance transmission in a C-band 7-core amplifier was achieved. This demonstration showed high-core count cladding pumped EDFAs are suitable for high throughput transmission over 1,000s km in both C and L band.

The results of this demonstration(1) were selected for presentation as a post-deadline paper at the 2019 Optical Fiber Conference (OFC 2019), the world’s largest event for optical communications research.

[Background]

Single mode, multi-core fibers (MCFs), multi-mode fiber, or a combination of both have been used in numerous high-capacity and long distance SDM transmission demonstrations(2). However, SDM technologies are also driven by the need for hardware integration and energy savings. As such, the successful development of SDM amplifiers is crucial for commercial realization of SDM technologies. In particular, large core-count cladding pumped multi-core erbium doped fiber amplifiers (MC-EDFAs) offer potential to integrate hardware(3) and significantly reduce the number of pump lasers respective to the number of spatial channels(4). Furthermore, such amplifiers are not only compatible with equivalent MCFs, but may also amplify several lower core-count MCFs, arrays of single-mode fibers or even signals from few-mode fibers. Previously large capacity was reached over short distances in a high-core count EDFA(5) and long distance transmission was achieved using a C-band 7-core amplifier(6). This demonstration showed high-core count cladding pumped EDFAs are suitable for high throughput transmission over 1,000s km in both C and L band, achieving the highest throughput-distance product of any SDM amplifier experiment of 1.44 Exb/s x km.

[Achievements]

The partners have performed a record data-throughput x distance experiment using an SDM amplifier. NICT constructed a recirculating transmission test-bed around the 19-core, cladding-pumped EDFA developed by Furukawa Electric.

The transmission system is made up from the following four main technologies.

• 19-core cladding pumped EDFA for C + L band transmission
• 19-core multi-core fiber and recirculating transmission set-up
• An optical frequency comb light source generating 345 wavelength channels
• PDM 16-QAM multi-level transmitter with 4 bit of data per symbol per wavelength

The amplifier was used to amplify signals in 19 cores simultaneously using two un-cooled multi-mode laser pumps per band. The combined pump power was 13.7 W and 43.5 W for the L-band and C-band EDFs respectively, equivalent to conversion efficiencies from electrical power of 40.3 % and 41.6 %.

[Future Prospects]

We are promoting R&D of innovative technology that achieves the early adoption of international standardization by industry-academia collaboration for establishing next-generation optical communication infrastructure technologies which can smoothly accommodate traffic for big data and 5G services. The results of this work were presented as a post deadline at the 2019 Optical Fiber Conference (OFC 2019), held in San Diego, USA from 3 to 7 March 2019.