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Future fronthaul wireless networks will be more competitive and attractive if they can use power- and cost-efficient transmitter systems to realize both extended reach and enhanced network capacity. Photonic generation of high-frequency RF carrier signals is currently considered an attractive technique. The laser gain-switching technique for photonic generation of high-frequency RF carrier signals has attracted great interest recently and is a cost-efficient scheme. Vertical cavity surface emitting laser (VCSEL) are power-efficient optical sources requiring bias currents below 10-mA. The use of VCSELs for gain-switched optical frequency comb generation has proven to be attractive in the term of power-efficiency. However, the data transmission performance of these gain-switched VCSEL optical frequency combs are yet to be demonstrated. In this paper, for the first time to our knowledge, we numerically demonstrated that RF carrier signals generated from a gain-switched VCSEL optical frequency comb can support up to16-Gbps error-free data transmission over fiber length beyond 20-km. A 56-GHz RF carrier signal was amplitude-modulated with 10- and 16.3-Gbps data before error-free transmission over 20.5-km of standard single mode fibers. Transmission penalties of 2- and 7-dB were recorded at 10- and 16.3-Gbps, respectively, at receiver sensitivities below -17-dBm.

This work reports on the use of a gain-switched vertical cavity surface-emitting laser (VCSEL) optical frequency comb (OFC) to generate multiple optical carriers for applications in future wavelength-division multiplexing (WDM) passive optical network (PON) systems. The VCSEL-based OFC system was tested for its ability to simultaneously transmit error-free data signals up to 30 Gbps, and a 50 MHz clock signal proposed to be used for latency monitoring of the network. The system was demonstrated over a fiber distance beyond 20 km. Four optical carrier signals were filtered from the generated OFC. Three of the four optical carriers were combined and amplitude-modulated with 5 and 10 Gbps on–off keying (OOK) data signals. The fourth optical carrier was amplitude-modulated with a 50 MHz clock signal. These four modulated optical carriers were multiplexed and transmitted over 21 km of standard single-mode fiber. When the three data-carrying optical carriers were modulated with 5 Gbps OOK data and multiplexed with the clock-carrying carrier, a negligible transmission penalty was achieved after fiber transmission. When these three data-carrying optical carriers were modulated with 10 Gbps OOK data and multiplexed with a clock-carrying carrier, a maximum transmission penalty of 4.8 dB was achieved after fiber transmission. The system was investigated at a minim bit error rate (BER) of 10 − 9 . A receiver sensitivity of less than − 11 d B m was achieved at both bit rates. The clock signal suffered little effect when transmitted with the three optical carriers at both 5 and 10 Gbps data rate. A power penalty of 15.37 dB, mainly due to fiber attenuation, was experienced in the clock after fiber transmission. Due to the unavailability of the numerical system to quantify the clock performance in terms of phase noise, the phase-noise results could not be provided. Nevertheless, the provided qualitative results were able to show that the transmitted clock integrity was able to be retained after being multiplexed with transmission on the 21 km fiber channel. For the first time, to the best of our knowledge, we have simultaneously reported on data and clock transmission results using a low-power, VCSEL-based OFC to realize a WDM-PON system. These results are attractive as they demonstrate and motivate the possibility of using gain-switched VCSELs as OFC sources in future WDM-PON networks requiring enhanced channel capacity and stringent network latency monitoring to realize intelligent, simple, and power-efficient PON networks.

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