UC Santa Barbara
Multi-wavelength Selective Crossbar Switch
- Author(s): Prabhu Khope, Akhilesh Sanjay
- Advisor(s): Bowers, John E.
- Saleh, Adel A. M.
- et al.
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