Record PM-16QAM and PM-QPSK transmission distance (125 and 340 km) over hollow-core-fiber

In this paper, 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/ 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/ penalty-free transmission over multiple bands, highlighting the potential of this fiber technology for high-speed short-to intermediate-reach applications.

Section: Discussionmentioning

confidence: 61%

Section: Introductionmentioning

confidence: 92%

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

Hong

Sakr

Taengnoi

et al. 2020

“…1 in which the delay change of 1-km long hollow-core photonics bandgap fiber (HC-PBGF) sample used in this study with temperature is shown, changing at a rate of 1.8 ps/ O C. It is worth mentioning that the latest generation HCFs have loss below 1 dB/km (recently-published record is 0.65 dB/km at 1550 nm [12]. They are manufactured in km lengths [13]. Further, they can have low chromatic dispersion (e.g., <3 ps/nm/km) and very low non-linearity (>2 orders of magnitude lower than SMF-28).…”

Section: Thermal Properties Of Standard and Hollow Core Fibersmentioning

confidence: 78%

Low Thermal Sensitivity Hollow Core Fiber for Optically-Switched Data Centers

Clark

Chen

Fokua

et al. 2020

Optical switches offer several benefits over electronics switches, including better scalability, lower power consumption, and lower latency. However, their implementation faces several challenges, including electronic transceivers to be able to support sub-nanosecond clock and data recovery time. This is required to efficiently handle data center traffic that is dominated by small data packets. Recent research shows that, scalable and sub-nanosecond data recovery can be achieved by synchronizing the clocks of all end-points connected to an optical switch in frequency and phase. In such a system, thermallyinduced change of propagation time through standard single mode fiber (SMF-28) necessitates the clock phases to be tracked due to variations in the data centers temperature. Hollow core fiber has been shown to have a thermal coefficient of delay 20 times smaller than SMF-28, offering potential to simplify the clock phase tracking and to increase the distance scale of data center networks. In this paper, we show how the low thermal coefficient of delay in hollow core fiber enables sub-nanosecond optical switching system with only initial frequency and phase synchronization. We obtained error-free real-time transmission of 60 ns packets over 1 km clock and 1 km hollow core data fiber with under 625 ps clock recovery time in both a point-to-point and a 2-to-1 optically switched 25.6 Gb/s real-time system. Based on our results, we estimate that sub-nanosecond clock recovery can be achieved for a 100 m size data center cluster interconnected by an optical switch using hollow core fiber, frequency synchronization and only a single phase calibration at the start-up.

“…The current record transmission length through NANF is 341 km, achieved by recirculating 71 times a PM-QPSK channel, operating at 32 GBaud, through a 4.8 km assembled line of NANF, with 7.5 dB loss. The channel sat at the center of a 61-channel WDM comb in the C-band and the record length was achieved at a pre-FEC BER of less than 3•10 −2 [11]. This result improved considerably over [7].…”

mentioning

confidence: 92%

Transmission of 61 C-Band Channels Over Record Distance of Hollow-Core-Fiber With L-Band Interferers

Nespola

Straullu

Bradley

et al. 2021

We report on two recirculating loop transmission experiments over a hollow-core fiber of the Nested-Antiresonant Nodeless type (NANF). We transmitted 61 channels in C-band at 32 GBaud, with either PM-QPSK or PM-16QAM modulation. In addition, 61 L-band interferers co-propagated in the NANF at all times, though they were not recirculated in the loop, to check for the presence of possible crosstalk effects between C and L-band in the NANF. The loop comprised the longest NANF transmission line yet constructed (7.72 km), as well as 55 km of pure-silicacore fiber (PSCF) needed to provide enough signal buffering and EDFA stabilization for the loop. The launch power into the PSCF was low enough to avoid generation of any significant non-linear noise. Using PM-QPSK, we achieved a record 618 km transmission in NANF (80 recirculations), at an overall average GMI of 3.44 bits/symb. Using PM-16QAM, we achieved a record 201 km transmission, at an overall average GMI of 7 bits/symb. We saw no adverse effect from the presence of L-band interferers in the NANF. If progress in the reduction of NANF loss and intermodal interference continues at the rate of the last few years, these hollow-core fibers might become a promising alternative in the quest for next-generation higher-throughput fibers, given their theoretical potential of achieving low loss and ultra-low nonlinearity over ultra-wide bandwidths, ideally bringing about a many-fold increase in throughput per fiber.