We experimentally demonstrate a net-rate 503.61-Gbit/s discrete multitone (DMT) transmission over 10-km 7-core fiber with 1.5-mu m single mode VCSEL, where low-complexity kernelrecursive-least-squares algorithm is employed for nonlinear channel equalization.
We report a method to determine propagation delays of optical 10 Gb/s data traveling through a 75 km long amplified fiber link with an uncertainty of 4 ps. The one-way propagation delay is determined by two-way exchange and cross correlation of short
(< 1 ms) bursts of 10 Gb/s data, with a single-shot time resolution better than 2.5 ps. We thus achieve a novel optical communications link suited for both long-haul high-capacity data transfer and time transfer with picosecond-range uncertainty. This opens up the perspective of synchronized optical telecommunication networks allowing picosecond-range time distribution and millimeter-range positioning.
We demonstrate the long-distance transmission of an ultra-stable optical frequency derived directly from a state-of-the-art optical frequency standard. Using an active stabilization system we deliver the frequency via a 146 km long underground fiber
link with a fractional instability of 3*10^{-15} at 1 s, which is close to the theoretical limit for our transfer experiment. The relative uncertainty for the transfer is below 1*10^{-19} after 30 000 seconds. Tests with a very short fiber show that noise in our stabilization system contributes fluctuations which are two orders of magnitude lower, namely 3*10^{-17} at 1 s, reaching 10^{-20} after 4000 s.
We demonstrate a remote microwave/radio-frequency (RF) transfer technique based on the stabilization of a fiber link using a fiber-loop optical-microwave phase detector (FLOM-PD). This method compensates for the excess phase fluctuations introduced i
n fiber transfer by direct phase comparison between the optical pulse train reflected from the remote site and the local microwave/RF signal using the FLOM-PD. This enables sub-fs resolution and long-term stable link stabilization while having wide timing detection range and less demand in fiber dispersion compensation. The demonstrated relative frequency instability between 2.856-GHz RF oscillators separated by a 2.3-km fiber link is $7.6 times 10^{-18}$ and $6.5 times 10^{-19}$ at 1000 s and 82500 s averaging time, respectively.
We demonstrate 1 Tbit/s/$lambda$ single-span transmission over a heterogeneous link consisting of graded-index 50 $mu$m core multi-mode fiber and 6LP few-mode fiber using a Kramers-Kronig receiver structure. Furthermore, the link budget increase by t
ransmitting only three modes while employing more than three receivers is investigated.
We report on two ultrastable lasers each stabilized to independent silicon Fabry-Perot cavities operated at 124 K. The fractional frequency instability of each laser is completely determined by the fundamental thermal Brownian noise of the mirror coa
tings with a flicker noise floor of $4 times 10^{-17}$ for integration times between 0.8 s and a few tens of seconds. We rigorously treat the notorious divergencies encountered with the associated flicker frequency noise and derive methods to relate this noise to observable and practically relevant linewidths and coherence times. The individual laser linewidth obtained from the phase noise spectrum or the direct beat note between the two lasers can be as small as 5 mHz at 194 THz. From the measured phase evolution between the two laser fields we derive usable phase coherence times for different applications of 11 s and 60 s.
Lu Zhang
,Joris Van Kerrebrouck
,Oskars Ozolins
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(2018)
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"Experimental Demonstration of 503.61-Gbit/s DMT over 10-km 7-Core Fiber with 1.5-mu m SM-VCSEL for Optical Interconnects"
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Xiaodan Pang
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