This paper reviews high-capacity space-division multiplexed (SDM) optical transport system technologies that support the evolution of broadband networks. Technologies that offer new spatial degrees of freedom such as core multiplexing and mode multiplexing can be introduced to optical transmission systems, optical switching systems, and optical fibers; they overcome the physical limits of today’s transport systems based on single-mode fibers. The expected features of future SDM-based optical transport networks are achieving both high transmission capacity over 1 Pbit/s and node throughputs above 10 Pbit/s, while reducing the power consumption and the size of transport node equipment.
We describe a computer generated hologram (CGH) method for application to a multiple input and multiple output (MxN) optical switch based on a liquid crystal on silicon (LCOS). The conventional MxN optical switch needs multiple spatial light modulations. However, the CGH method realizes an MxN optical switch simply with a one-time spatial light modulation, resulting in fewer optical elements and better cost efficiency. Moreover, the intrinsic loss of the proposed MxN switch resulting from beam splitting can be reduced by routing multiple signals with a single knob control, which is called a multi-pole multi-throw switch. In this paper, we demonstrate a 5x5 wavelength selective switch (WSS) and a 2-degree ROADM that we realized using the above CGH method. The experimental results indicate that these switches work well with a crosstalk of < -14.9 dB.
A high port count wavelength selective switch (HPC-WSS) is a key component when constructing colorless, directionless, and contentionless ROADM because it provides increased flexibility and scalability. We have been developing HPC-WSSs by combining a waveguide-based optical frontend and free-space optics, which we call a spatial and planar optical circuit (SPOC) platform. In this paper, we present an HPC-WSS and a low-loss transponder aggregator based on a SPOC platform, and we also describe the reliability of the frontend, which is a key enabler for the SPOC platform.
We propose and demonstrate Ternary Phase-Shift-Keying Modulation as a novel countermeasure for the backscattering induced noise in micro optic gyro (MOG) on silica planar lightwave circuit (PLC), whose thermo-optic phase modulator has limited bandwidth of only ∼ 1KHz.
In this paper, we report a novel configuration of micro optic gyro (MOG), which is monolithically integrated on silica Planar Lightwave Circuit (PLC) with countermeasures for noise factors. Optical ring-resonator gyros suffer mainly form polarization fluctuation induced noise and backscattering induced noise. We adopt a stress applying amorphus silicon film as the countermeasure for the former, and binary phase shift keying (b-PSK) as the one for the latter. However, to apply b-PSK, thermo-optic (TO) phase modulation is the only one scheme available in silica waveguide, whose bandwidth is limited to approximately 1 KHz. To utilize the narrow bandwidth of the TO modulator effectively, we propose an electrical signal processing scheme and frequency compensating modulation waveform. We demonstrate the suppression of the backscattering induced noise as 7.6dB. Additionally the gyro output is observed with applying an equivalent rotation.
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