Electro-optically tunable laser with ultra-low tuning power dissipation and nanosecond-order wavelength switching for coherent networks

The huge amount of data traffic behind the rapid growth of cloud computing is putting pressure on the operation of mobile fronthauls and data center networks so there is a need to improve their power consumption and latency. We developed an electro-optically tunable laser diode employing a tunable filter that is practically tuned even with small refractive index change of the electro-optic effect. The laser shows a small tuning power dissipation of less than 10 mW for a practical tuning range of over 35 nm with a linewidth of about 350 kHz. We also achieved high-speed optical switching of less than 50 ns for 100 Gb/s coherent signals. In addition to its application in optical communications, the electro-optically tunable laser diode is also beneficial to laser sensing applications because its higher tuning speed increases the time resolution of the sensing system. Furthermore, a narrow linewidth, conventionally difficult to reconcile with high-speed tuning, can also enable a longer sensing distance and/or a higher signal-to-noise ratio when using coherent detection. Our result shows that we can use the electro-optic effect to overcome the limitations of conventional tunable laser diodes and drastically change optical communications and laser sensing systems.

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also one-to-on ween q and m ng β 0 δlq involv q).We need som ination which out the β 0 δlq an q), we can rewri s follows.shifts (reflectance change of the RTF).We assume the threshold currents and its fluctuation are mainly determined by an excess loss of the RTF (5dB) and its loss fluctuation (+/-1.5 dB) for a round-trip [1,2], respectively.The loss fluctuation is caused by the wavelength dependence of the MMI and imperfection of waveguide fabrication.When we apply the above excess loss value, the RTF cavity length (~1.5 mm) and other typical laser parameters including a linewidth enhancement factor (<5) to a theoretical model [8], the expected laser linewidth is less than 300 kHz.So, we believe that the limiting factor of the RTF laser linewidth (~350 kHz) is not the cavity loss but another one such as electrical noises from the experimental set up to ACT and tuning electrodes.

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