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Multi-wavelength Selective Crossbar Switch


Switches are used to connect servers together to form a network in datacenters and

in telecommunication. This can be done with electronic switches or optical switches.

There has been a tremendous effort in the optics community to miniaturize switches with

integrated photonic technology. Many of these switches are single wavelength switches,

i.e they connect two ports with a single wavelength channel. These switches under utilize

the channel bandwidth provided by Wavelength Division Multiplexing.

In this thesis, I propose a multi-wavelength selective switch that can dynamically

assign multiple channels for any connection. Such a switch can help scale data centers

and drastically reduce cabling complexity. The theory of the switch is developed and

measurements of the switch fabricated in a Silicon photonics foundry are reported. A

novel on-chip locking mechanism for the switches is also proposed and demonstrated.

We measured an average path loss of 10 dB on Gen III 8x4 switch with a standard

deviation of 2 dB. These losses were reduced by a factor of 4 in Gen IV 4x4 switch

with undoped ring resonators to 2.65 dB with a standard deviation of 1.35 dB. The

tuning range of the rings is twice the Gen III 8x4 switch and the Gen IV 4x4 switch

is tunable across 4 channels at 400 GHz spacing. We measured a 10 to 90 % large

signal switching time of 15 s. Multiple input Bit Error Rate measurements showed

negligible power penalty due to incoherent crosstalk. Ring resonators are also locked to

two channels spaced at 100 and 200 GHz using an on-chip photodetector in an on-chip

locking experiment.

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