Thomas Jensen, Eckart Witzel, Alexandre Paduch,Patrick Ziegler, E.U. Wagemann, and Oliver Funke

Agilent Technologies GmbH, Herrenberger Straße 130, 71034 Böblingen,Germany

NFOEC, Dallas 2002

A new method to determine Loss, PDL, GD,and DGD of passive optical components

NFOEC Dallas 2002 Page 2

Outline

• Optical Network Evolution• Experimental Setup• Measurement Principles for Loss, PD, GD, and DGD• Accuracy Verification• Measurement Examples• Summary

NFOEC Dallas 2002 Page 3

Optical Network Evolution

DeMUX

OADM

VOAGain eq.

∆τ∆τ∆τ∆τ

CD / PMDcompensator

MUX λλλλ

OA

Next Generation optical network facts:• 40 Gb/s and beyond• ultra dense WDM (≤≤≤≤10 Gb/s)• transparent

Network performance strongly depends on both: • amplitude (loss) and • phase (dispersion) characteristics of optical components

����

NFOEC Dallas 2002 Page 4

Complex component designs require an adequateall-parameter test method

Advanced components require high resolution andhigh accuracy for both loss and dispersion test

Example: TFF-Design

(G.Lenz et.al., IEEE J. Quant. Electr., 1390 (1998)

NFOEC Dallas 2002 Page 5

Experimental Setup

Swept homodyne interferometry

SignalLocal oscillator

Pol.contr.8169A

TLS81640B

DUTE D F

G

H

I

J

Wavelength Reference Unit

NFOEC Dallas 2002 Page 6

Loss & PDL Determination• Application of four well-known

polarization states to the DUT

• Transmission data are used to calculate the1st row - Mueller matrix coefficients

• PDL is obtained from the Mueller matrix coefficients

0

0.1

0.2

0.3

0.4

0.5

0.6

1533 1533.2 1533.4 1533.6 1533.8 1534 1534.2 1534.4 1534.6 1534.8 1535Wavelength

PDL

Scanning 10msScanning 1msMueller Method

accuracy comparablewith polarization scanning method

NFOEC Dallas 2002 Page 7

GD & DGD Determination

Interferometric principle

Polarizationresolvingdetector

Tunable laser &polarization controller

DUT

Interferometer

)(cos)()(2)()()( ,22

, ωϕωωωωω jidutLOdutLOji EEEEP ⋅++=

Polarization resolved measurement based on two orthogonalsweeps i and detections j .

NFOEC Dallas 2002 Page 8

Calculation from Jones matrixTransformation of the eigenvectors 2/1x� of the DUT Jones matrix

)()()()()( 2/12/1)(

2/12/12/1 ωωωωσω ωφ xUxey i ���

⋅=⋅=

2/1)(

2/12/1 )(

)(1

2/1 xUex i �� ⋅���

����

�= − ω

ωσωφ

Eigenvectors do not depend on the wavelength

2/12/1

2/12/1

22/1

2/12/1 '11'0 2/12/12/1 xUeUeiUedxd iii �

�

⋅���

����

�+−−== −−− φφφ

στ

σσσ

ω .

Simplification to an eigenvalue relation( ) 2/12/12/12/1

',0' τσσγγ iwithxUU +==⋅−

�

Calculation of GD and DGD from the eigenvalues

( ))Im()Im(21)(

)Im()Im()(

21

21

γγω

γγω

+=

−=

GD

DGD

NFOEC Dallas 2002 Page 9

Comparison of measured and theoretical GDcurve of HCN gas cell peak

1547 1547.2 1547.4 1547.6 1547.8 1548

5

10

15

20HCN gas cell

wavelength [nm]

grou

p de

lay

[ps]

red: measurementblue: theory

Theoretical curve reconstructed with Kramers-Kronig relationfrom amplitude response .

deviationbelow 1%

NFOEC Dallas 2002 Page 10

Comparison of DGD measurement with NIST

Averaged DGD results on NIST SRM 2518 / 029

0.32

0.34

0.36

0.38

0.4

0.42

0.44

1520.5-1568.5nm 1531.5-1568.5nm

DG

D [p

s]NISTinstrument a

instrument b

NIST device consist of coupled waveplates.DGD value is averaged over wavelength interval (PMD 1st order).

NFOEC Dallas 2002 Page 11

Measured DGD repeatability (i.e. TFF)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

1555.3 1555.4 1555.5 1555.6 1555.7 1555.8 1555.9 1556 1556.1 1556.2

DG

D p

s

0

5

10

15

20

25

loss

dB

NFOEC Dallas 2002 Page 12

Noise contribution of setup

0 20 40 60 80 1000.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

2σdg

d [p

s]

averages

sliding window 10 pm 30 pm 50 pm

0 20 40 60 80 1000.00

0.01

0.02

0.03

0.04

0.05

2σgd

[ps

]

averages

sliding window 10 pm 20 pm 30 pm 50 pm

• GD • DGD

Number of averages and width of sliding window have to be set properlyfor required SNR and spectral resolution.

NFOEC Dallas 2002 Page 13

Measurement of Dispersion Compensator (FBG)

• Reflection • Transmission

1574.0 1574.4 1574.8 1575.20

500

1000

1500

2000

2500

3000

3500

GD

IL

GD

[ps

]

wavelength [nm]

-40

-30

-20

-10

0

1573.0 1573.5 1574.0 1574.5 1575.0 1575.5 1576.00

5

10

15

20

25

30

35

GD

IL

wavelength [nm]

-15

-10

-5

0

IL [dB]

NFOEC Dallas 2002 Page 14

Measurement of Thin-Film-Filter

1572.6 1572.8 1573.0 1573.2012345

DGD

DG

D [

ps]

wavelength [nm]

0102030405060

GD

GD

[ps

]

-50-40-30-20-10

0IL

IL [

dB]

NFOEC Dallas 2002 Page 15

Measurement of AWG

1552.8 1553.2 1553.6 1554.0 1554.40

10

20

30

40

DGD

DG

D [

ps]

wavelength [nm]

50

100

150 GD

GD

[ps

]

-60-50-40-30-20-10

0PDLIL

IL [

dB]

024681012 PD

L [dB]

NFOEC Dallas 2002 Page 16

Measurement of EDFA

1530 1540 1550 1560 15700.0

0.2

0.4

0.6

0.8DGD

DG

D [

ps]

wavelength [nm]

0

2

4

6

8

GD

GD

[ps

]

-25-20-15-10

-5 ILIL

[dB

]

NFOEC Dallas 2002 Page 17

Summary

• In this presentation we reported on a new measurement method fortesting passive components for spectral loss, PDL, GD, and DGD.

• When moving to advanced networks (beyond 10G or ultra-dense)requirements to test all-parameters can be expected for manycomponents.

• All-parameter test combines the state-of-the-art technique for Lossand PDL with a new high potential interferometric GD and DGDmeasurement.

• The new measurement method demonstrates its potentialparticularly when characterizing advanced network components