100Tbs Optical Routers: Optics Overview

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100Tb/s Optical RoutersOptics Overview

• Kyoungsik Yu
• Stanford University
• Stanford, CA, USA

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Optics in Optical Router Overview

• Parameters (assuming 10Gbps link)
• Wavelength W32
• MEMS switches M50
• Linecard groups G25

1600 links/group
40,000 links
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Outline

• Optical power budget
• Volume/Housing
• Modulation
• Optical Multiplexing/Demultiplexing
• MEMS switches
• Connection between optical elements
• Cost

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Loss Budget

• External Modulation vs Direct modulation
• -42dB power loss for external modulation
• 17dBm CW-DFB is commercially available
• Can be driven more than one laser

-17dB for direct modulation
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External modulation

• 1x50 power splitter
• 10cmx9cmx2cm
• lt0.5W power consumption
• W32 power splitters per group
• 6,000cm3 (18cm)3
• 10Gb/s modulator
• 8cmx2cmx1cm
• WxM1600 modulators per group
• 26,000cm3 (30cm)3

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Direct Modulation

• 1 laser per link ? 1600 lasers per group
• 10Gb/s short reach transceiver module
• 1310nm, -1dBm, DFB
• -14dBm sensitivity APD
• SMF pigtailed
• 8cmx6cmx2cm
• 157,000cm3 (54cm)3
• 4W ? 6.4kW per group

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How large are multiplexers?

• 1x32 wavelength multiplexers
• 10cmx6cmx2cm ? 12,000cm3
• 5dB insertion loss
• 2xM100 MUXDMUX per group
• 2xMxW 3200 fibers per group ? Corner turner?

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How large are MEMS switches?

• 32x32 MEMS switches
• 20cmx28cmx4cm
• 112,000cm3 for 25 groups
• lt0.5W power consumption
• 7dB insertion loss
• 50 MEMS switches in one rack

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How can we connect them?

• One group (25 linecards) in one rack
• 50 fibers from one rack (group)
• 1250 fibers in, 1250 fibers out

Fiber shuffle network
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Optics in Optical Router Overview

• Parameters (assuming 10Gbps link)
• Wavelength W32
• MEMS switches M50
• Linecard groups G25

1600 links/group
40,000 links
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How much are they?

• MEMS switches (2-D MEMS)
• Assuming 100/port
• Mx(GG)x1000.25 Million
• Wavelength (de)multiplexers
• Assuming 100/port
• 2xGxMxWx1008 Million
• External optical modulators (MZ, LiNbO3)
• Assuming 2000/10G (?)
• GxMxWx200080 Million

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Modulator Array

• Noahs modulator

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Optical Demultiplexer Array

• Surface normal devices can be easily integrated
  into array
• Grating with 1-D and 2-D fiber array
• AWGs dont scale well because of wafer size

Array of AWGs
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Gires-Tournois Interferometer

• Oblique incident angle
• Optical beams are spatially separated
• Enables phase shift of individual beams
• Free Spectral Range (FSR) proportional to 1/d.
• FSR corresponds to the WDM channel spacing

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MEMS Implementation

• Phase modulation on each outgoing beam
• Simple up-and-down motion for phase shift
• lt1mm is sufficient for 2p phase shift at l 1.55
  mm

WYKO measurement of MEMS mirror array
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Tunable Center Wavelength

• Amplitude Determined by beam splitter
• Phase determined by micromirror position

?1 ?2 ?30 0 0
?1 ?2 ?3? 2? 3? ? 0 ?
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Tunable Optical Bandwidth

• Center frequency, free spectral range (FSR), and
  filter shape can be adjusted by moving the MEMS
  mirrors

?1 ?2 ?3? ? ?
Near field pattern
Far field pattern
?1 ?2 ?30 0 0
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Channel Spacing Tunability

• The channel spacing is controlled by the spacing
  of the beam splitter and the micromirror array

20dB Crosstalk
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MEMS GTI Tunable (De)Interleaver

• Uniform displacement of micromirror array

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MEMS GTI Dispersion Compensator

• Tunable dispersion compensator with 200GHz FSR
  (equals WDM channel spacing)
• A MUMPs four-mirror array with 200um mirrors and
  3um gaps was used
• Measured dispersion tuning range -130ps/nm to
  150ps/nm as shown
• Passband gt 0.32nm (40GHz, i.e. the bandwidth
  utilization was 20)
• Insertion loss variation within the passband lt
  4.6dB
• Worst-case fiber-to-fiber insertion loss
  14.8dB (mostly due to fiber misalignment)

Only one period is shown
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GTI Optical Demultiplexer
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Experimental Setup
Tunable Laser
MEMS Mirror Array
Input fiber
Power Detector
Output Fiber
Beam Splitter
Focusing Optics
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Switching Characteristic

• Oscilloscope capture of dynamic characteristics

Input Signal to MEMS
Output Optical Signal
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MEMS Mirror Characteristics

• 1.2mm deflection for 150V
• Natural frequency 15kHz
• Rise time 20ms

WYKO measurement data for single MEMS mirror
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Project Plans

• Complete characterization of SOI mirror
• Push-pull signaling for faster mirror response
• Optical experiments
• Tunable bandwidth optical filter
• 1x5 optical demultiplexer/multiplexer
• Optical CDMA encoder/decoder with 5 users
• Develop packaged GTIs for system demonstrations
• Design and fabricate improved micromirror arrays
• High-speed operation (goal 100 ns switching
  times)