Dissipative Kerr soliton microcombs for FEC-free optical communications over 100 channels

Abstract

The demand for high-speed and highly efficient optical communication techniques has been rapidly growing due to the ever-increasing volume of data traffic. As well as the digital coherent communication used for core and metro networks, intensity modulation and direct detection (IM-DD) are still promising schemes in intra/inter data centers thanks to their low latency, high reliability, and good cost performance. In this work, we study a microresonator-based frequency comb as a potential light source for future IM-DD optical systems where applications may include replacing individual stabilized lasers with a continuous laser driven microresonator. Regarding comb line powers and spectral intervals, we compare a modulation instability comb and a soliton microcomb and provide a quantitative analysis with regard to telecom applications. Our experimental demonstration achieved a forward error correction (FEC) free operation of bit-error rate (BER) <10−9 with a 1.45 Tbps capacity using a total of 145 lines over the entire C-band and revealed the possibility of soliton microcomb-based ultra-dense wavelength division multiplexing (WDM) with a simple, cost-effective IM-DD scheme, with a view to future practical use in data centers.

Applications for optical frequency microcomb chips

“…First, the performance of optical microcombs has been continually improving in terms of its spectral bandwidth, energy efficiency, phase coherence, and stability, and this has significantly enhanced their performance in these applications. Secondly, optical microcombs have become more widely used for traditional and demanding applications, such as frequency synthesis [20][21][22][23][24][25][26][27][28], spectral filtering [29][30][31][32][33], temporal signal processing [34][35][36][37][38][39][40], and optical communications [33,[41][42][43][44][45]. Finally, many new and exciting interdisciplinary applications have emerged, spanning the frontiers of light detection and ranging (LiDAR) [46][47][48][49], astronomical detection [50][51][52][53], neuromorphic computing [54][55][56], and quantum optics [11,57,58], which bring significant new opportunities.…”

“…In addition to coherent optical communications, optical microcombs have been used as multiwavelength sources for IM-DD optical communications [33,45]. In contrast to coherent optical communications that achieve high sensitivity needed for long-distance communications, the IM-DD optical communication systems have a reduced complexity that that is advantageous for short-distance communications in local area networks where low latency and low cost are important [45].…”

“…In an alternative approach based on bulk-optic microcombs, IM-DD optical communications over 40 km has been demonstrated based on optical microcombs generated by a MgF2 crystalline microresonator with an FSR of ~10 GHz (Figure 16(a)) [45], where 145 comb lines covering the entire C-band were employed as the optical carriers of the WDM channels. A maximum data rate of ~1.45 Tbit/s and a maximum SE of ~1 bit/s/Hz were experimentally achieved, together with a BER < 10 -9 for an operation without using the FEC.…”

Soliton microcombs in whispering gallery mode crystalline resonators with broadband intermode interactions

“…Soliton microcombs based on optical microresonators have triggered the rapid development of miniature and chip scale optical frequency combs in recent years [1][2][3][4], and have resulted in the emergence of fully integrated frequency comb chips, opening an access to high-performance, high-compactness, and high-volume laser sources for advanced optical metrology [5][6][7][8][9]. Indeed, a number of proof-of-concept applications have been demonstrated with soliton microcombs, such as massive parallel optical communications [10,11], optical ranging [12][13][14], massive parallel LIDAR [15], low-noise microwave synthesis [16][17][18], astronomical spectral calibration [19,20], and optical nuerophomic computing [21,22].…”

“…While recent focus is on photonic integrated platforms where wafer scale, high quality and highly nonlinear optical microresonators are accessible [23], a parallel platform is whispering gallery mode (WGM) based crystalline resonators [24,25]. In particular, crystalline fluoride resonators could have a recordhigh finesse beyond 10 7 [26], which is suitable for the genera-tion of ultra-narrow linewidth lasers [27][28][29][30] as well as soliton microcombs [1,11,[31][32][33]. Given a weak thermo-refractive noise, such resonators could support solitons with low-noise repetition frequencies, serving as a photonic microwave synthesizer [16,17].…”