wdm optical interfaces for future fiber radio systems phần 10 pps

Chapter 6: Integration of Millimetre-Wave Fibre-Radio Networks in WDM

Optical Access Infrastructure

The modulated signals were then applied to the AWG, as shown in Fig. 6. 7. The

allocation of the input ports and the selection of the loop-back paths are maintained

in such a way that the resultant output of the AWG is the desired interleaved signals.

Fig. 6.9 shows the combined spectrum of the signals after multiplexing, which

confirms the functionality of the proposed H-MUX, enabling wavelength

interleaving for the modulated multiband signals in an integrated DWDM access

network. The spectrum also indicates that the multiplexing of the signals using such

CRF SRF

Wavelength (nm)

-70

1555.9 1556.3 1556.7

-10

Optical Po

w

er (dBm)

-30

-50

(a)

BB

Wavelength (nm)

-70

1555.9 1556.3 1556.7

-10

Optical Po

w

er (dBm)

-30

-50

(b)

IF

Wavelength (nm)

-70

1555.9 1556.3 1556.7

-10

-30

-50

(c)

CRF SRF

Wavelength (nm)

-70

1555.9 1556.3 1556.7

-10

Optical Po

w

er (dBm)

-30

-50

(a)

CRF SRF

Wavelength (nm)

-70

1555.9 1556.3 1556.7

-10

Optical Po

w

er (dBm)

-30

-50

(a)

BB

Wavelength (nm)

-70

1555.9 1556.3 1556.7

-10

Optical Po

w

er (dBm)

-30

-50

(b)

BB

Wavelength (nm)

-70

1555.9 1556.3 1556.7

-10

Optical Po

w

er (dBm)

-30

-50

BB

Wavelength (nm)

-70

1555.9 1556.3 1556.7

-10

Optical Po

w

er (dBm)

-30

-50

(b)

IF

Wavelength (nm)

-70

1555.9 1556.3 1556.7

-10

-30

-50

(c)

IF

Wavelength (nm)

-70

1555.9 1556.3 1556.7

-10

-30

-50

(c)

Fig. 6.10: Measured optical spectra for the recovered: (a): RF, (b): BB and (c): IF signals at the

OADM interface.

255

Chapter 6: Integration of Millimetre-Wave Fibre-Radio Networks in WDM

Optical Access Infrastructure

H-MUX reduces the CSR of optical RF signal to 5 dB, attaining an effective

reduction by 8 dB.

The composite signal was then amplified by an erbium-doped-fibre-amplifier

(EDFA) and followed by a 4-nm optical band pass filter (BPF) prior to transmission

over 10 km of singlemode fibre(SMF) to a BS, where each of the multiplexed signals

was recovered using a suitable optical add-drop-multiplexing (OADM) interface.

The OADM interface, which is comprised of a double-notch tunable fibre Bragg

grating (FBG) and a 3-port optical circulator, recovers each of the signals separately

1555.8 1556.2 1556.6

Wavelength (nm)

0

-40

-30

-20

Optical P

o

w

er (dBm)

-10

SRF

CRF IF

(b)

0

-40

-30

-20

-10

1555.8 1556.2 1556.6

Wavelength (nm)

SRF

BB CRF

(c)

0

-40

-30

-20

Optical P

o

w

er (dBm)

-10

1555.8 1556.2 1556.6

Wavelength (nm)

BB IF

(a)

1555.8 1556.2 1556.6

Wavelength (nm)

0

-40

-30

-20

Optical P

o

w

er (dBm)

-10

SRF

CRF IF

(b)

1555.8 1556.2 1556.6

Wavelength (nm)

0

-40

-30

-20

Optical P

o

w

er (dBm)

-10

SRF

CRF IF

(b)

0

-40

-30

-20

-10

1555.8 1556.2 1556.6

Wavelength (nm)

SRF

BB CRF

(c)

0

-40

-30

-20

-10

1555.8 1556.2 1556.6

Wavelength (nm)

SRF

BB CRF

(c)

0

-40

-30

-20

Optical P

o

w

er (dBm)

-10

1555.8 1556.2 1556.6

Wavelength (nm)

BB IF

(a)

0

-40

-30

-20

Optical P

o

w

er (dBm)

-10

1555.8 1556.2 1556.6

Wavelength (nm)

BB IF

(a)

Fig. 6.11: Measured optical spectra for the signals passing through while recovering: (a): RF, (b):

BB and (c): IF signals using the OADM interface.

256

Chapter 6: Integration of Millimetre-Wave Fibre-Radio Networks in WDM

Optical Access Infrastructure

from the interleaved signals by shifting the centre frequencies of the FBG. The

spectra of recovered signals can be seen from Fig. 6.10 (a) - (c).

The spectra for the signals passing through the OADM interface are also shown in

Fig. 6.11 (a)-(c). The optical spectra shown in Fig. 6.10 and 6.11 indicate that the

recovered signals are contaminated by unwanted -24 dB to -30 dB optical crosstalk,

which however, can be further minimised by proper selection of the FBG comprising

the OADM interface.

-6

-7

-8

-9

-17.4 -17 -16.6 -16.2 -15.8 -15.4

RF Signal with

Data Rate 155Mb/s

10 KM SMF

0.0 KM SMF

ol g10 (B

E

R)

Received Optical Power (dBm)

(a)

-6

-7

-8

-9

-22.5 -22 -21.5 -21 -20.5 -20 -19.5

10 KM SMF

0.0 KM SMF

ol g10 (B

E

R)

Received Optical Power (dBm)

Baseband Signal with

Data rate 1Gb/s

(b)

-6

-7

-8

-9

-29.2 -28.8 -28.4 -28 -27.6

IF signal with

Data Rate 155Mb/s

10 KM SMF

0.0 KM SMF

Received Optical Power (dBm)

(c)

-6

-7

-8

-9

-17.4 -17 -16.6 -16.2 -15.8 -15.4

RF Signal with

Data Rate 155Mb/s

10 KM SMF

0.0 KM SMF

ol g10 (B

E

R)

Received Optical Power (dBm)

-6

-7

-8

-9

-17.4 -17 -16.6 -16.2 -15.8 -15.4

RF Signal with

Data Rate 155Mb/s

10 KM SMF

0.0 KM SMF

ol g10 (B

E

R)

Received Optical Power (dBm)

(a)

-6

-7

-8

-9

-22.5 -22 -21.5 -21 -20.5 -20 -19.5

10 KM SMF

0.0 KM SMF

ol g10 (B

E

R)

Received Optical Power (dBm)

Baseband Signal with

Data rate 1Gb/s

-6

-7

-8

-9

-22.5 -22 -21.5 -21 -20.5 -20 -19.5

10 KM SMF

0.0 KM SMF

ol g10 (B

E

R)

Received Optical Power (dBm)

Baseband Signal with

Data rate 1Gb/s

(b)

-6

-7

-8

-9

-29.2 -28.8 -28.4 -28 -27.6

IF signal with

Data Rate 155Mb/s

10 KM SMF

0.0 KM SMF

Received Optical Power (dBm)

-6

-7

-8

-9

-29.2 -28.8 -28.4 -28 -27.6

IF signal with

Data Rate 155Mb/s

10 KM SMF

0.0 KM SMF

Received Optical Power (dBm)

(c)

Fig. 6.12: Measured BER curves as a function of received optical power for: (a): RF, (b): BB, and

(c): IF signals recovered from the three wavelengths interleaved multiband signals after

transmission over 10 km SMF, with the back to back curves as the reference.

257