# Single channel 100 Gbit/s link in the 300 GHz band

Vinay Kumar Chinni, Philipp Latzel, Malek Zegaoui, Christophe Coinon, X.

Wallart, Emilien Peytavit, Jean-Francois Lampin, Klaus Engenhardt, P.

Szriftgiser, Mohammed Zaknoune, et al.

► To cite this version:

Vinay Kumar Chinni, Philipp Latzel, Malek Zegaoui, Christophe Coinon, X. Wallart, et al. Single channel 100 Gbit/s link in the 300 GHz band. 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), Sep 2018, Nagoya, Japan. 10.1109/IRMMW-THz.2018.8510070. [hal-03286178](https://hal.science/hal-03286178)

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https://hal.science/hal-03286178

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Distributed under a Creative Commons Attribution 4.0 International License
Single channel 100 Gbit/s link in the 300 GHz band

V.K. Chinni<sup>a</sup>, P. Latzel<sup>a</sup>, M. Zégaoui<sup>a,b</sup>, C. Coinon<sup>a</sup>, X. Wallart<sup>a</sup>, E. Peytavit<sup>a</sup>, J.F. Lampin<sup>a</sup>, K.

Engenhardt<sup>c</sup>, P. Szriftgiser<sup>d</sup>, M. Zaknoune<sup>a</sup>, G. Ducournau<sup>a</sup>

<sup>a</sup> Institut d'Electronique, de Microélectronique et de Nanotechnologie, Univ. Lille, CNRS, Centrale
Lille, ISEN, Univ. Valenciennes, UMR 8520 - IEMN, F-59652 Villeneuve d'Ascq, France.

<sup>b</sup> IRCICA USR-3380, avenue Halley 59658 Villeneuve d'Ascq cedex

<sup>c</sup> Tektronix GmbH, Heinrich-Pesch-Straße 9-11, 50739 Köln, Germany

<sup>d</sup> Laboratoire de Physique des Lasers Atomes et Molécules (PhLAM), UMR CNRS 8523, Université
Lille 1, F-59655 Villeneuve d'Ascq Cedex, France

***Abstract***— We report on the achievement of single channel 100 Gbit/s transmission, using linear resonant cavity enhanced unitravelling carrier photodiodes and QAM-16 modulation format. The indoor wireless link has been validated for up to 100 Gbit/s and 280 GHz carrier frequency.

## I. INTRODUCTION AND BACKGROUND

Since 10 years, significant efforts enable to reach technological breakthrough towards > 40 Gbit/s wireless communications in the THz bands [1], and a new standard has been established by the IEEE [2]. Photonics-based solutions, are intrinsic wideband and linear due to the photomixing process, with output powers up to the mW range [3]. We demonstrate in this paper the use of these photodiodes for 100 Gbit/s data-rates at 280 GHz.

## II. UTC-PD PERFORMANCE

The structure and topology of the UTC-PD used in this experiment has been reported recently [3]. This photodiode is using a semitransparent top contact with subwavelength apertures for enhanced optical transmission, front-side illumination of the photodiode (1.55 µm wavelength), featuring a good trade-off between optical responsivity and RF electrical losses (the metallic layer of the top contact is not covering the full UTC-PD mesa). The responsivity of the device is further increased by using a metallic mirror below the diode mesa through wafer bonding. The DC response of the UTC-PD (4 µm diameter) used here is 0.1 A/W. The available power at UTC-PD output is given by the figure 1.

<figure><img src="image_2.png" /><figcaption>**Fig. 1** Output power of the RCE UTC-PD at carrier frequency (280 GHz). Inset: view of the probed device. Left: fibre holder to illuminate the device, and right: coplanar probe in 220-325 GHz range.</figcaption></figure>

## III. DATACOM RESULTS

The figure 2 is presenting the experimental setup used to establish the 300 GHz datalink. The system is composed of optical modulation in QAM-16 (Quadrature Amplitude Modulation) obtained by driving optical modulator with two PAM (Pulsed Amplitude Modulation) with 4 levels and 25 GBaud. This signal is converted into the THz range using a UTC-PD photomixer, and further detected by a sub-harmonic mixer (SHM), followed by a wideband oscilloscope for detection and constellation analysis.

<figure><img src="image_3.png" /><figcaption>**Fig. 2.** Experimental setup. RCE-UTC-PD: Resonant Cavity Enhanced Photodiode. EDFA = Erbium Doped Fiber Amplifier.</figcaption></figure>
The constellations of THz transmission at 56, 80 and 100 Gbit/s data rate are shown in the figure 3. A very linear QAM-16 is detected, up to 100 Gbit/s data rates. The blue points correspond to the decision instants, and the green curves behind are the signal path between two decision instants. It can be seen that in any case, the QAM-16 constellation is clearly shown, with an increase of the noise level due to the decrease of the signal to noise ratio at highest data-rates.

<figure><img src="image_4.png" /><figcaption>**Fig. 3** Constellations examples obtained at the end of the THz link. Photodiode (-1 V bias) current level was 4.9 mA for 56 Gbit/s, 5.1 mA for 80 Gbit/s and 5.3 mA for 100 Gbit/s, using 23 taps for digital equalization.</figcaption></figure>

The figure 4 shows the results of the highest data-rate tested, precisely 100 Gbit/s. The digitally processed Bit Error Rate (BER) evolution is given with current inside the photodiode. At 100 Gbit/s, BER down to $10^{-6}$ have been reached with this photodiodes, over a half-meter link distance (limited by the lab configuration).

<figure><img src="image_5.png" /><figcaption>**Fig. 4.** BER performances achieved for up to 100 Gbit/s with tap number used at the receiver.</figcaption></figure>

## CONCLUSION

Using linear UTC-PD, we have reported the demonstration of a single 100 Gbit/s THz channel using QAM-16 signaling, compliant to the new IEEE standard for 100 Gbit/s wireless communications in the 300 GHz bands [2].

## ACKNOWLEDGMENTS

This work was supported by Equipex programs ‘FLUX’, ‘EXCELSIOR’, ANR ‘COM'TONIQ’, Era-net ‘TERALINKS’, ANR-DFG ‘TERASONIC’ projects. Part of the work was realized under an academic collaboration with

Tektronix. In particular, a 50GS/s arbitrary waveform generator (Tektronix AWG70001A)" and ,,200GS/s real-time oscilloscope (Tektronix DPO77002SX) were used. We also thank the IEMN, characterization centre, IEMN-IRCICA Telecom platform facilities. This work is supported by the CPER ‘Photonics for society’, and contribute the “digital world” Hub 3 of the I-Site Université de Lille Nord de France.

## References

[1] T. Nagatsuma et al., “Advances in terahertz communications accelerated by photonics”, Nature Photon., vol. 10, pp. 371–379, 2016, doi: 10.1038/nphoton.2016.65.

[2] IEEE Standard for High Data Rate Wireless Multi-Media Networks-- Amendment 2: 100 Gb/s Wireless Switched Point-to-Point Physical Layer," in IEEE Std 802.15.3d-2017 (Amendment to IEEE Std 802.15.3-2016 as amended by IEEE Std 802.15.3e-2017), vol., no., pp.1-55, Oct. 18 2017.

[3] P. Latzel et al., "Generation of mW Level in the 300-GHz Band Using Resonant-Cavity-Enhanced Unitraveling Carrier Photodiodes," IEEE Trans. on Terahertz Science and Technology, vol. 7, no. 6, pp. 800-807, Nov. 2017.