Some Practical Issues in Deep-Time Multiplexing

Managed and operated by

National Security Technologies, LLC

2016 Photonic Doppler Velocimetry Workshop: June 6–9, 2016

Some Practical Issues in Deep-Time Multiplexing

Michael PeñaDefense Experimentation and Stockpile Stewardship


This work was done by National Security Technologies, LLC, under

Contract No. DE-AC52-06NA25946 with the U.S. Department of Energy.

DOE/NV/25946--2857




► Deep-time multiplexing

■ Conceptual design

► Index of refraction variations

■ Wavelength

■ Temperature

► State of Polarization

■ Stability

■ Control

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Outline




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Deep-Time Approach ROADDM

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

800μs record at detector

= 10km SMF (50us)

16 signals fromMPDV,

2 per ITU21-35

~150km SMF

DW

DM

DW

DMNS

2x2

DW

DM

2x1 PD

80km SMF

SCOPE

8 Local Oscillators1 per ITU21-35

Corning® SMF-28® Ultra

αmax ≤ 0.18 dB

km

Dλ ≤ 18.0 𝑝𝑠

(nm·km)

Neff : 1.4682

Pol. Ctrl

► Reconfigurable Optical Add Drop “Delay” Module




• Index of Refraction, n(λ)

• Phase Velocity, 𝑣𝑝𝜔

𝑘

𝑐𝑜

𝑛(λ)

• Group Velocity, 𝑣𝑔𝑑𝜔

𝑑𝑘; 𝑑λ=

−λ2

2𝜋𝑐𝑜𝑑𝜔

𝑐𝑜

𝑛(λ) 1 −λ𝑛

𝑑𝑛

𝑑λ

−1

• Group Velocity Dispersion, GVD𝑑2𝑘

𝑑𝜔2λ3

2𝜋𝑐𝑜2

𝑑2𝑛

𝑑λ2

• Group Delay, 𝜏𝑔 =𝐿

𝑣𝑔=𝑑𝜑

𝑑𝜔

𝑑𝜑

𝑑𝜔=𝑑 𝑘𝐿

𝑑𝜔

𝑛

𝑐𝑜1 −λ𝑛

𝑑𝑛

𝑑λ 𝐿

• Group Delay Dispersion, GDD𝑑𝜏𝑔

𝑑𝜔=𝑑2(𝑘𝐿)

𝑑𝜔2λ3

2𝜋𝑐𝑜2

𝑑2𝑛

𝑑λ2 𝐿

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Wavelength-Dependent Index of Refraction

18𝑝𝑠

𝑛𝑚 ∙ 𝑘𝑚× 10[𝑘𝑚] × 1560.61 − 1549.32 [𝑛𝑚]

= 2.032𝑛𝑠

18𝑝𝑠

𝑛𝑚 ∙ 𝑘𝑚× 150[𝑘𝑚] × 1560.61 − 1549.32 [𝑛𝑚]

= 30.483𝑛𝑠




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Modulation Phase Shift Dispersion Measurement

Tunable

Laser

Intensity

ModulatorPD

Sine Wave

Generator

Compare phase

DUT

fm

∆𝜏𝑔 𝜆 =𝜑 𝜆 − 𝜑 𝜆𝑟360°

1

𝑓𝑚

𝐷 𝜆 =1

𝐿

𝑑 ∆𝜏𝑔 𝜆

𝑑𝜆=

1

360°𝐿𝑓𝑚

𝑑𝜑 𝜆

𝑑𝜆

Measurement setup for fiber chromatic dispersion

Δτ(λ) = 0.00029598λ2 – 0.7348λ + 440.16

Δτ(1560.61nm) - Δτ(1549.32nm) = 1.97305ns

𝐷λ =1973.05𝑝𝑠

11.29𝑛𝑚∙10𝑘𝑚= 17.476

𝑝𝑠

𝑛𝑚∙𝑘𝑚




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Temperature-Dependent Index of RefractionLUNA Technical Note EN_FY1406,

∆𝜏

𝜏=1

𝐿

𝜕𝐿

𝜕𝑇∆𝑇 +1

𝑛

𝜕𝑛

𝜕𝑇∆𝑇 = 𝛼𝐿 + 𝛼𝑛 ∆𝑇

αL : thermal expansion coeff 𝛼𝑛 : thermo-optic coeff0.55 x 10-6 °C-1 ~7.0 to 9.0 x 10-6 °C-1

(7.5 x 10-6 used below)

385𝑝𝑠

℃ ∙ 10𝑘𝑚∙ 15 𝑑𝑒𝑙𝑎𝑦𝑠 = 5.78

𝑛𝑠

℃

210𝑝𝑠

℉ ∙ 10𝑘𝑚∙ 15 𝑑𝑒𝑙𝑎𝑦𝑠 = 3.15

𝑛𝑠

℉

Observed temps.

y=0.393x -8.644

y=0.3798x -8.769




In situ Cross-Timing Mark

-7-

XT-mark

XT-mark in each time window

Follow temp-time fluctuations

XT-mark inherently same λ as

velocity record

Single XT-mark for 16 records (only

8 shown)

Temperature fluctuations ~1–16 ns

Temp gradients = inconsistent 𝛿t Compounded effect deeper in time

𝑛=1

15

𝛿𝑡𝑖𝛿𝑡𝑖

DW

DM

DW

DM

2x1




Static Signal Fluctuations

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• All channels seeing same

probe

• 30 m jumpers to firing

chamber

• Shot-to-shot variability

~10 dB




► Real single-mode fibers exhibit elliptical birefringence due to

■ Deviations of core shape from circularity

■ Lateral compression

■ Residual twist

■ Bending

-9-

Polarization/Induced Birefringence

y

x

y

x

F

F

Core ellipticity Compression Twist Bending




-10-

Stokes Parameters vs. 50 min

𝜏8

𝜏1

LO21




-11-

Tau Windows 1 through 8

(1 millisecond)




-12-

Tau Windows 9 through 16

(1 millisecond)Stressed Fiber?

Increasing variations




Local Oscillator SOP

(1 millisecond)

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-14-

Aligning Local Oscillators with Signals

𝑄𝑊1 =𝜋

2𝑄𝑊2 =

5𝜋

3𝑄𝑊3 =

𝜋

3𝑄𝑊4 =

𝜋

3

Dot Products (Signal,LO)

𝜏1 = 0.3546 𝜏9 = 0.8797 ITU21

𝜏2 = 0.4207 𝜏10 = 0.3000 ITU23

𝜏3 = −0.1510 𝜏11 = 0.7326 ITU25

𝜏4 = 0.5092 𝜏12 = 0.7100 ITU27

𝜏5 = −0.3259 𝜏13 = 0.8980 ITU29

𝜏6 = 0.2449 𝜏14 = 0.5950 ITU31

𝜏7 = 0.8789 𝜏15 = 0.2652 ITU33

𝜏8 = −0.8642 𝜏16 = 0.7807 ITU35

−1 ≤ 𝑆𝑖𝑔𝑛𝑎𝑙 ∙ 𝐿𝑂 ≤ 1● Signal ▲ Local Oscillator




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Polarization Controllers – Fiber Squeezers (EPC-300)

Linear Horizontal

𝑆𝑜𝑢𝑡 = 𝑀0°45°0°45°

100

Linear +45

𝑆𝑜𝑢𝑡 = 𝑀0°45°0°45°

010

45°45°

0°0°

Right Circular

𝑆𝑜𝑢𝑡 = 𝑀0°45°0°45°

001

► Not all inputs are affected equally!




-16-

Polarization Controllers – PolarRITE (VarRotQWP)

Linear Horizontal

𝑆𝑜𝑢𝑡 = 𝑀𝜃,𝜑

100

Right Circular

𝑆𝑜𝑢𝑡 = 𝑀𝜃,𝜑°

001

Linear +45

𝑆𝑜𝑢𝑡 = 𝑀𝜃,𝜑

010




-17-

Polarization Controllers 3-Paddle (RQW-RHW-RQW)

Linear +45

𝑆𝑜𝑢𝑡 = 𝑀𝜃1,𝜃2,𝜃3

010

Linear Horizontal


100

Right Circular


001




► Solution to current systems will need to be:

■ Single- or few-point solution

■ Endless tracking (i.e., no reset or operation discontinuity)

■ Feedback loop, detection and compensation

● System time constants ~seconds

● Dynamic excursions from experiment

■ Practical

● Ease of use

● Cost

● Physical footprint

► Looking at all-optical solutions

■ Based on nonlinear interactions

● Raman, four-wave mixing, SBS

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Still a work in progress




► Timing issues

■ Wavelength- and temperature-dependent Index of Refraction

● ~ 21𝑝𝑠

℉∙𝑘𝑚/ ~38

𝑝𝑠

℃∙𝑘𝑚

■ In situ timing marks follow time variations

► State of Polarization

■ Each time window will have unique state

■ SOP distribution increases with time

■ SOP relatively stable over ~1 hr and ~100s μs

■ Polarization controllers effect SOPs differently

Questions?

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Conclusion

Documents

Some Practical Issues in Deep-Time Multiplexing