analysis of multi-channel crosstalk with soa as pre- … security level: huawei technologies co.,...

www.huawei.com

Security Level:

HUAWEI TECHNOLOGIES CO., LTD.

Analysis of Multi-channel

Crosstalk with SOA as Pre-

amplifier in 100G EPON

Ting Yang, Dekun Liu

May, 2017

HUAWEI TECHNOLOGIES CO., LTD. 2

Background

Due to the lower receiver sensitivity at 25Gb/s line rate and the

extra loss of mux/demux, 100G EPON high likely needs optical

pre-amplifiers to meet the PR30 power budget requirement .

From both implementation and cost consideration, 4 channels of

100G share a same pre-amp SOA is a more practical solution.

Due to the fast carrier recovery time in SOA, when multiple

channels share a same SOA, some crosstalk between channels

will happen.

This contribution study the crosstalk effect between channels

when a shared pre-amp SOA is used for 100G EPON and shows

some initial experiment results.


Experimental setup

25G EML

Tx1

25G EML

Tx2

DATA1

DATA2D

EM

UX

Error

Detector

25G PIN/APD

Rx1

50:50

Coupler

DE

MU

X

Optical

power meter

Attenuator

Error

Detector

25G PIN/APD

Rx1

SO

A

50:50

Coupler

Electrical path

Optical path

Electrical path

Optical path

1294.6 nm, ER=8.5dB 1299.9 nm, ER=8 dB 1308.3 nm, ER=9.5dB


Sensitivity of 25G APD & 25G PIN

-28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8

10

9

8

7

6

5

4

3

2

25G APD

25G PIN

-Lo

g1

0(B

ER

)

Received power [dBm]

Parameter Value Unit

Tx bit rate 25.78125 Gb/s

Tx wavelength 1294.6 nm

Tx output power 2 dBm

Tx ER 8.5 dB

Rx responsivity APD: 3~6

A/W PIN: 0.75

Rx sensitivity

(@BER=1E-3)

APD: -25.9 dBm

PIN: -17.2

Test conditions: back-to-back, NRZ, PRBS=2^31-1


Transmission spectra of filter

CWDM Filter

LAN-WDM Filter

1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350-60

-50

-40

-30

-20

-10

0

10

No

rma

lize

d [d

B]

Wavelength [nm]

1290 nm

1288 1292 1296 1300 1304 1308 1312 1316-60

-50

-40

-30

-20

-10

0

10

No

rma

lize

d [d

B]

Wavelength [nm]

1295.56 nm

For input power of -25 dBm, crosstalk power of -9 dBm

For input power of -28 dBm, crosstalk power of -9 dBm


Case1: 25G APD with CWDM filter

-32 -30 -28 -26 -24 -22 -20 -18 -16 -14 -12

10

9

8

7

6

5

4

3

2

w/o crosstalk

w crosstalk, -29 dBm


w crosstalk, -9 dBm

-Lo

g1

0(B

ER

)


25G APD w/o crosstalk w. crosstalk

power of -29 dBm

w. crosstalk

power of -19 dBm

w. crosstalk

power of -9 dBm

Rx. Sen.

(@BER=1E-3) -25.9 dBm -29.8 dBm -29.5 dBm -29.3 dBm -25.3 dBm

25G APD ROSA, SOA 120mA 45degC

λ1 (test signal)

λ1

λ2

λ2 (crosstalk signal)

Pre-amp Rx

CWDM Demux

DE

MU

X

Error

Detector

25G PIN/APD

Rx1

DE

MU

X

Error

Detector

25G PIN/APD

Rx1SO

A

50:50

Coupler

1270 nm

1330 nm

1290 nm

1310 nm


Case2: 25G PIN with CWDM filter

-30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10

10

9

8

7

6

5

4

3

2

w/o crosstalk



w crosstalk, -9 dBm

-Lo

g1

0(B

ER

)


25G PIN ROSA, SOA 120mA 45degC

25G PIN w/o crosstalk w. crosstalk

power of -29 dBm

w. crosstalk

power of -19 dBm

w. crosstalk

power of -9 dBm

Rx. Sen.


λ1 (test signal)

λ1

λ2


Pre-amp Rx

CWDM Demux

DE

MU

X

Error

Detector

25G PIN/APD

Rx1

DE

MU

X

Error

Detector

25G PIN/APD

Rx1SO

A

50:50

Coupler

1270 nm

1330 nm

1290 nm

1310 nm


Case3: 25G APD with LAN-WDM filter

-34 -32 -30 -28 -26 -24 -22 -20 -18

10

9

8

7

6

5

4

3

2

w/o crosstalk



w crosstalk, -9 dBm

-Lo

g1

0(B

ER

)


25G APD ROSA, SOA 120mA 45degC

25G APD w/o crosstalk w. crosstalk

power of -29 dBm

w. crosstalk

power of -19 dBm

w. crosstalk

power of -9 dBm

Rx. Sen.


λ1 (test signal)

λ1

λ2


Pre-amp Rx

LAN-WDM Demux


Case4: 25G PIN with LAN-WDM filter

-32 -30 -28 -26 -24 -22 -20 -18 -16 -14

10

9

8

7

6

5

4

3

2

w/o crosstalk



w crosstalk, -9 dBm

-Lo

g1

0(B

ER

)


25G PIN ROSA, SOA 120mA 45degC

25G PIN w/o crosstalk w. crosstalk

power of -29 dBm

w. crosstalk

power of -19 dBm

w. crosstalk

power of -9 dBm

Rx. Sen.


λ1 (test signal)

λ1

λ2


Pre-amp Rx

LAN-WDM Demux


Overview comparison

w/o SOA w/o crosstalk w. crosstalk

power of -29 dBm

w. crosstalk

power of -19 dBm

w. crosstalk

power of -9 dBm

25G APD

Rx. Sen.

(@BER=1E-3)

-25.9 dBm -29.8 dBm -29.5 dBm -29.3 dBm -25.3 dBm

25G PIN

Rx. Sen.

(@BER=1E-3)


CWDM case

w/o SOA w/o crosstalk w. crosstalk

power of -29 dBm

w. crosstalk

power of -19 dBm

w. crosstalk

power of -9 dBm

25G APD

Rx. Sen.

(@BER=1E-3)


25G PIN

Rx. Sen.

(@BER=1E-3)


LAN-WDM case


Summary

When multiple channels share a same pre-amp SOA:

The crosstalk penalty for other channels is less than 1dB if

the input power of crosstalk channel is comparable with

that of the test channel.

If the input power of crosstalk channel is distinctly higher

than that of test channel (such as 20dB more), there will

be serious crosstalk penalty.


Analysis:

The gain of SOA will decrease as the total input power increases.

In worst case, the total power of λ1,λ2,λ3 can be 24dB higher than λ4.

(14dB ODN dynamic range, 5dB ONU launch power spread range together

with log10(3) )

Such a big dynamic range in PON upstream will be the killer for the shared

pre-amp SOA used in OLT for upstream.

SOA Gain vs Input power

Gai

n

Bias current

If three strong signal together with one weak signal arrive the OLT at the same time, the SOA will become saturated and can’t provide enough gain for weak signal


How to solve this issue?


It needs more SOA gain due to the insertion loss of Demux

For discrete components solution:

Cost is very high, size is very big, heat dissipation is vey challenging

For optical integration solution:

Narrow band filter is very difficult to design

Both filter and SOA must be polarization insensitive

Size and heat dissipation is very challenging

Technical maturity is poor

Solution (1)-single channel SOA

SOA filter Rx

SOA filter Rx

SOA filter Rx

SOA filter Rx

Dem

ux

Narrow band

It’s not a good solution for commercialization in foresee near term


Solution(2) –single domain DBA

All 4 sub-channels in a single scheduling domain

This will result in huge bandwidth wasting

guo_3ca_3_0516.pdf


Final thoughts:

There still be a lot of issues on the feasibility of

100G EPON pre-amp SOA to overcome the

needed power budget issue.

The task force need to decide which way we

should go or explore some more potential

solutions.

Thank you www.huawei.com

analysis of multi-channel crosstalk with soa as pre- … security level: huawei technologies co.,...

Documents