Semiconductor Optical Amplifiers in Avionics

C Michie, W Johnstone , I Andonovic , E Murphy , H White, A Kelly

Semiconductor Optical Amplifiers in Avionics

• Significant advantages within Avionics context from use of optical communications networks • bandwidth, EMI, significant weight savings

• Current systems limited to point to point, multimode

• This work• Learn from terrestrial communications using COTS• Focus on PONs – cost is critical• Strategies towards WDM – minimal component inventory

• Key operational consideration• Extended temperature range

Long Haul; DWDM systems maximise fibre bandwidth

usageTXλ1

TXλ2

TXλN

TXλX

TXλX

TXλX

TXλX

40 wavelengths, 200 GHz spacing10,40, 100+ Gbit/channel

Long Haul; DWDM systems maximise fibre bandwidth

usage• Wavelength specific transmitters

– single wavelength, DFB– Temperature regulated

• Many wavelengths– inventory issues for Avionic system

• Temperature Control– increased power consumption

• Expensive for Avionics– not a flier!

Passive Optical Networks

• High bandwidth Access solutions• Cost is critical – minimise number of components• Minimise manufacturing specification• Operate without cooling if possible

• Reflective Semiconductor Based Optical Amplifiers– RSOA – transmitter and amplifier using same

component

CS- RSOA

RSOAs as transmitters

User end

BLS

P

λ

P

λ

CS-RSOA

RSOAs as transmitters

User

Broad Band Source

P

λ

P

BLS

CS-RSOA

CS-RSOA

CS-RSOA

Avionics Link

• Simple link– 500 m, 1 Gbit/s

• Single Broad band seed source– might need two ?

• Multiplexer, de-multiplexer• Minimal cooling/heating

BLS

Fibre Link

Tx RSOA

Tx RSOA

Tx RSOA

Tx RSOA

Rx

Rx

Rx

Rx

Fibre Link Tx RSOA

Tx RSOA

Tx RSOA

Tx RSOA

Rx

Rx

Rx

Rx

0.6 dB

0.6 dB

0.8 dB3.5 dB

RSOA Design

InP:InGaAsPBuried HeterostructureLateral Waveguide TapersTensile Bulk

High back refectivity 0.88

Front facet AR coated

RSOA in TO

TO-packaged S-band RSOA TO-packaged S-band RSOA parametric testsparametric tests

Standard tests at 25ºC and 80mA

Dynamic Range

• Psat ~ 5 dBm, Gain > 20 dB• so we need -15 dBm input to saturate• Can get 0dBm/nm from COTS sources

• -5 dBm/nm is obtainable with lower power module– NB the above module needs to be cooled but it should

be the only component within the system• To get 12 dB dynamic range (allows 3dB plus of

margin) we can allow gain/Psat drop with temperature

RSOA modulation experimentsRSOA modulation experiments

TO packaged devices on ETS evaluation board50mA DC bias, 60mA modulation S band RSOA, CW injection at 1465 – 1530nmStage temperature 25°CModulation at 1.25 Gbps data rate with 211-1 PRBS bit patternThe Rx - APD photoreceiver with limiting amplifier

Sensitivity, Output Power, Gain and Path Sensitivity, Output Power, Gain and Path Loss Capability at 1490nm and 25Loss Capability at 1490nm and 25ºCºC

~30dB return path loss capability at -20dBm input

Sensitivity, Output Power, Gain and Path Sensitivity, Output Power, Gain and Path Loss Capability at 1580nm and 25Loss Capability at 1580nm and 25ºCºC

Sensitivity, Output Power, Gain and Sensitivity, Output Power, Gain and PLC versus Wavelength at 25PLC versus Wavelength at 25ºCºC

-20dBm CW input power and 25ºC stage temperatureEye diagram at 1490nm

S, C and L band performanceS-band device C-band device

-40

-30

-20

-10

0

10

20

30

40

1440 1460 1480 1500 1520 1540 1560 1580 1600 1620 1640

Wavelength (nm)

Se

ns

itiv

ity(d

Bm

),P

ou

t(d

Bm

),P

LC

(dB

),G

ain

(dB

)

Sens

Pout

Gain

PLC

RSOA with Broadband light source

Path Loss Capability TLS, BlS

0

5

10

15

20

25

30

35

40

-30 -25 -20 -15 -10 -5

Input Power (dBm)

Po

we

r B

ud

ge

t (d

B)

-35

-30

-25

-20

-15

-10

-5

0

Se

ns

itiv

ity

(dB

)

Margin BLS 0.5 nm

Margin TLS

BLS Sens 0.5 nm

TLS Sens

High Temperature RSOA Design

AlInGaAs Ridge WaveguideSingle Polarisation

High back refectivity 0.88

Front facet AR coated 0.01%

RSOA in TO

Temperature Performance of RSOA

TuneableLaser RSOA

OpticalSpectrum Analyser

VariableAttenuator

Temperature Controlled

Mount

Evaluate Gain, NF, Psat as a function of temperature.Enables prediction of performance(Power budget for BER 10-9)

Packaged BH Temperature Characterisation

Chip on CarrierRidge Temperature

Characterisation

Temperature Characterisation

Conclusions

• WDM PONs enabled by RSOAs–TO packaged polarisation insensitive S band RSOA – ~1dB penalty at 1.25Gbit/s compared to commercial M-Z modulator

• High Temperature OperationAlInGaAs active region

–Ridge waveguide design due to oxidation–Single polarisation –Potential to increase operating temperature to > 70 C–Much reduced cooling requirement