Experimental results and discussion

Figure 5-10 illustrates the electrical spectrums for QPSK OFDM signals and Figure 5-11. BER curves of the OFDM QPSK signals

Figure 5-10. Electrical Spectrums of QPSK OFDM signals.

(a) Tx OFDM and subcarrier electrical spectrum.

(b) OFDM electrical spectrum after I/Q modulator.

(c) Rx OFDM electrical spectrum.

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indicates where the spectrums belong to. Inset (a) of Figure 5-10 is the electrical spectrum of transmitter terminal OFDM signals and 12GHz-subcarrier. Inset (b) of Figure 5-10 is the one of OFDM signals after I/Q modulator. We can see the bandwidth is 7GHz. And Inset (c) of Figure 5-10 is the electrical spectrum of receiver QPSK OFDM signals. We down convert the signals to center frequency 5GHz.

Figure 5-12 shows QPSK constellation diagrams before and after the frequency quadrupling system in back-to-back (BTB) and following SMF transmission cases.

The equalizer in OFDM transceiver is used to combat both frequency response of various millimeter-wave components at 60 GHz and fiber dispersion. Since the proposed OFDM transmitter can generate high-purity two-tone lightwave, the generated OFDM signals do not suffer from periodic fading issue due to fiber dispersion. Only in-band distortion of the OFDM-encoded subcarrier induced by fiber dispersion is considered. Since the symbol rate of each subcarrier is only 156.25 MSym/s, the fiber chromatic penalty can be ignored. Figure 5-11 shows the BER curves of the 14-Gb/s QPSK OFDM signals using optimal OPRs after transmission over 100-km SMF. After transmission 100-km, the sensitivity penalties is about 1dB.

Compare purple circular symbols with red diamond symbols, the penalty of frequency quadrupling system is 2dB. Although it still worsens the performance a little, it does better than using electrical mixer with noise figure (NF) 8dB. Inset (a), (b), (c) and (d) of Figure 5-12 are BTB before frequency quadrupling, BTB, 50km and 100km, respectively. They are captured at PD input power equal to -11dBm.

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Figure 5-12. Constellations of QPSK OFDM signals (-11dBm).

(a) BTB before 4f (b) BTB (c) 50km (d) 100km

Figure 5-13. Electrical Spectrums of 20Gb/s 16-QAM OFDM signals.

(a) Tx OFDM and subcarrier electrical spectrum.

(b) Rx OFDM electrical spectrum.

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Figure 5-13 illustrates the electrical spectrums for 20Gb/s 16-QAM OFDM signals and indicates where the spectrums belong to. Inset (a) of Figure 5-13 is the electrical spectrum of transmitter terminal OFDM signals and 12GHz-subcarrier. Inset (b) of Figure 5-13 is the electrical spectrum of receiver 16-QAM OFDM signals. The bandwidth is 5GHz. We down convert the signals to center frequency 5GHz.

Figure 5-15 shows 16-QAM constellation diagrams after the frequency quadrupling system in back-to-back (BTB) and following SMF transmission cases.

The equalizer in OFDM transceiver is used to combat both frequency response of various millimeter-wave components at 60 GHz and fiber dispersion. Since the proposed OFDM transmitter can generate high-purity two-tone lightwave, the generated OFDM signals do not suffer from periodic fading issue due to fiber dispersion. Only in-band distortion of the OFDM-encoded subcarrier induced by fiber dispersion is considered.

Figure 5-14. BER curves of the 20Gb/s OFDM 16-QAM signals using DFB Laser.

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Figure 5-15. Constellations of 20Gb/s 16-QAM OFDM signals using DFB Laser (-5dBm). (a) BTB (b) 25km (c) 50km (d) 75km (e) 100km

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Since the symbol rate of each subcarrier is only 156.25 MSym/s, the fiber chromatic penalty can be ignored. Figure 5-14 shows the BER curves of the 20-Gb/s 16-QAM OFDM signals using optimal OPRs and DFB Laser after transmission over 100-km SMF. After transmission 100-km, the sensitivity penalties is very large. The reason to explain large penalty is laser line-width. Following pages will show you a better result with smaller line-width light source. Inset (a), (b), (c), (d) and (d) of Figure 5-15 are BTB, 25km, 50km, 75km and 100km, respectively. They are captured at PD input power equal to -5dBm.

Figure 5-16. Electrical Spectrums of 20Gb/s 16-QAM OFDM signals with tunable laser (TL).

(a)Tx OFDM and subcarrier electrical spectrum.

(b)Rx OFDM electrical spectrum.

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Figure 5-16 illustrates the electrical spectrums for 20Gb/s 16-QAM OFDM signals with tunable laser and indicates where the spectrums belong to. Inset (a) of Figure 5-16 is the electrical spectrum of transmitter terminal OFDM signals and 12GHz-subcarrier. Inset (b) of Figure 5-16 is the electrical spectrum of receiver 16-QAM OFDM signals. The bandwidth is 5GHz. We down convert the signals to center frequency 5GHz.

Figure 5-18 shows 16-QAM constellation diagrams after the frequency quadrupling system in back-to-back (BTB) and following SMF transmission cases.

The equalizer in OFDM transceiver is used to combat both frequency response of various millimeter-wave components at 60 GHz and fiber dispersion. Since the proposed OFDM transmitter can generate high-purity two-tone lightwave, the generated OFDM signals do not suffer from periodic fading issue due to fiber dispersion. Only in-band distortion of the OFDM-encoded subcarrier induced by fiber Figure 5-17. BER curves of the 20Gb/s OFDM 16-QAM signals using Tunable Laser.

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dispersion is considered. Since the symbol rate of each subcarrier is only 156.25 MSym/s, the fiber chromatic penalty can be ignored. Figure 5-17 shows the BER curves of the 20-Gb/s 16-QAM OFDM signals using optimal OPRs and DFB Laser after transmission over 100-km SMF. After transmission 100-km, the sensitivity penalties is almost negligible. The two cases only have one difference, laser line-width.

We replace DFB Laser with Tunable Laser to reduce light source line-width. Inset (a), (b), (c), (d) and (d) of Figure 5-18 are BTB, 25km, 50km, and 100km, respectively.

They are captured at PD input power equal to -5dBm.

Figure 5-18. Constellations of 20Gb/s 16-QAM OFDM signals using Tunable Laser (-5dBm).

(a) BTB (b) 25km (c) 50km (d) 100km

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Figure 5-19 illustrates the electrical spectrums for 28Gb/s 16-QAM OFDM Figure 5-19. Electrical Spectrums of 28Gb/s 16-QAM OFDM signals with tunable laser (TL).

(a) Tx OFDM and subcarrier electrical spectrum.

(b) Rx OFDM electrical spectrum.

Figure 5-20. BER curves of the 28Gb/s OFDM 16-QAM signals using Tunable Laser.

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signals with tunable laser and indicates where the spectrums belong to. Inset (a) of Figure 5-19 is the electrical spectrum of transmitter terminal OFDM signals and 12GHz-subcarrier. Inset (b) of Figure 5-19 is the electrical spectrum of receiver 16-QAM OFDM signals. The bandwidth is 7GHz. We down convert the signals to center frequency 5GHz.

Figure 5-21 shows 16-QAM constellation diagrams before and after the one-tap equalizer in back-to-back (BTB) and following SMF transmission cases. The equalizer in OFDM transceiver is used to combat both frequency response of various millimeter-wave components at 60 GHz and fiber dispersion. Since the proposed OFDM transmitter can generate high-purity two-tone lightwave, the generated OFDM signals do not suffer from periodic fading issue due to fiber dispersion. Only in-band distortion of the OFDM-encoded subcarrier induced by fiber dispersion is considered.

Since the symbol rate of each subcarrier is only 156.25 MSym/s, the fiber chromatic penalty can be ignored. Figure 5-20 shows the BER curves of the 28-Gb/s 16-QAM OFDM signals using optimal OPRs after transmission over 100-km SMF. The sensitivity penalties due to the fiber transmission are negligible. They are captured at PD input power equal to -4dBm.

By using all-optical up-conversion and frequency quintupling, we demonstrate 16-QAM OFDM signal generation and transmission with a record of 28 Gb/s within 7-GHz license-free spectrum at 60 GHz band. Transmission over 100-km SMF

transmission with negligible penalty is achieved without any dispersion compensation.

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Figure 5-21. Constellations of 28Gb/s 16-QAM OFDM signals using Tunable Laser (-5dBm).

(a) BTB w/o E.Q. (b) BTB (c) 50km (d) 100km

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Chapter 6 Conclusion

This work proposes a brand new modulation approach to generate optical vector signal by all optical up-conversion based on a modified SSB scheme. Since all optical up-conversion technique is used, the proposed system does not need high speed components at transmitter terminal compare with conventional modulation scheme using external modulator, and the system can generate direct detection vector signal.

This system provides a solution that can satisfy the demand of 60GHz application within 7GHz license-free band.

Since the proposed DD-OFDM transmitter needs no mixer with a typical NF of more than 8 dB to avoid the beat noise interference after detection, it has a great potential to support multi-level format (i.e. 16 QAM or 64 QAM) OFDM signal for narrow applications beyond 10 Gb/s. Error free (10^-9) of 10-Gb/s 16-QAM OFDM signal is demonstrated and negligible penalty is observed after 125-km SMF transmission. We also demonstrate 16-QAM OFDM signal generation and

transmission with a record of 28 Gb/s within 7-GHz license-free spectrum at 60 GHz band. Transmission over 100-km SMF transmission with negligible penalty is

achieved without any dispersion compensation.

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Babiel, and D. Jäger, “60GHz Radio-over-Fibre Wireless System for Bridging 10Gb/s Ethernet Links,” ECOC2008, Tu.3.F.6 (2008).

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OFC2008, OThP5 (2008).

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Appendix Publication International Journals and Conferences:

1. Chun-Ting Lin, Po-Tsung Shih, Wen-Jr Jiang, Er-Zih Wong, Jason(Jyehong) Chen, and Sien Chi, “Vector Signal Generation at Microwave/Millimeter-wave Bands Employing Optical Frequency Quadrupling Scheme,” to be published Optics Lett..

2. J.-W. Shi, F.-M. Kuo, Y.-S. Wu, Nan-Wei Chen, Po-Tsung Shih, Chun-Ting Lin, Wen-Jr Jiang,Er-Zih Wong, Jason (Jyehong) Chen, and Sien Chi, “A W-Band Photonic Transmitter-Mixer Based on High-Power Near-Ballistic

Uni-Traveling-Carrier Photodiodes for BPSK and QPSK Data Transmission under Bias Modulation,” to be published at IEEE Photon. Technol. Lett.

3. Chun-Ting Lin, Wen- Jr Jiang, Jason (Jyehong) Chen, Po Tsung Shih, Peng-Chun Peng, Er-Zih Wong, and Sien Chi, “Novel Optical Vector Signal Generation with Carrier Suppression and Frequency Multiplication Based on a Single-Electrode Mach-Zehnder Modulator,” IEEE Photon. Technol. Lett., Vol. 20, No. 24, pp.

2060-2062, Dec. 2008.

4. Wen-Jr Jiang, Chun-Ting Lin, Er-Zih Wong, Po-Tsung Shih, Jason(Jyehong) Chen, and Sien Chi, “A Novel Optical Direct-Detection I/Q Up-Conversion with I/Q Imbalance Compensation via Gram-Schmidt Orthogonalization Procedure”, European Conference and Exhibition on Optical Communication (ECOC 2009).

5. Chun-Ting Lin, Er-Zih Wong, Wen-Jr Jiang, Po-Tsung Shih,

6. Po-Tsung Shih, Chun-Ting Lin, Wen-Jr Jiang, Er-Zih Wong, Jason (Jyehong) Chen1, Sien Chi, Y.-S. Wu, F.-M. Kuo, Nan-Wei Chen, Jin-Wei Shi, “W-Band Vector Signal Generation via Optical Millimeter-Wave Generation and Direct Modulation of

Jason(Jyehong) Chen, and Sien Chi, “28-Gb/s 16-QAM OFDM Radio-over-Fiber System Within 7-GHz License-Free Band at 60 GHz Employing All-Optical Up-conversion,” Conference on Lasers and Electro-Optics (CLEO), 2009, post deadline paper CPDA8, Baltimore U.S.A.

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NBUTC-PD,” OFC 2009, paper OWP4, San Diego, U.S.A.

7. Chun-Ting Lin, Wen- Jr Jiang, Er-Zih Wong, Sheng-Peng Dai, Jason(Jyehong) Chen, Yu-Min, Lin, Po Tsung Shih, Peng-Chun Peng, and Sien Chi, “Experimental

Demonstration of Optical 5-Gb/s 16-QAM OFDM Signal Generation and Wavelength Reuse for 1.25-Gbit/s Uplink Signal” ECOC 2008, Brussels Expo., Belgium.

8. C. T. Lin, W. J. Jiang, E. Z. Wong, J. Chen, P. T. Shih, P. C. Peng, S. Chi, “Optical Vector Signal Generation Using Double Sideband with Carrier Suppression and Frequency Multiplication”, CLEO/QELS 2008, paper CThR5, San Jose, U.S.A.

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Vita

Er-Zih Wong

Contact Information:

Phone: 0916916107

Address: No.14, Ren-ai St., Fongyuan City, Taichung County 42044, Taiwan (R.O.C.) E-mail: shoko369896@hotmail.com

Education:

• M.S: Electro-Optical Engineering, National Chiao Tung University, Taiwan. (Sept. 2007 ~ present, Degree Expected: July 2009)

Advisors: Associate Prof. Jason (Jyehong) Chen; Prof. Sien Chi;

• B.S., Department of Electrophysics, National Chiao Tung University, Taiwan.

(Sept. 2003 ~ Jun. 2007);

Professional Skills and Contributions:

• Design and implementation of highest capacity hybrid access network:

28-Gb/s 16-QAM OFDM Radio-over-Fiber System Within 7-GHz License-Free Band at 60 GHz Employing All-Optical Up-conversion (CLEO post-deadline paper CPDA8)

• Optical millimeter-wave (60 GHz ~ 130 GHz) signal generation.

Vector Signal Generation at Microwave/Millimeter-wave Bands Employing Optical Frequency Quadrupling Scheme (Optics Lett., OFC, ECOC)

• High spectrum efficiency modulation format (OFDM, QAM ect.).

Experimental Demonstration of Optical 5-Gb/s 16-QAM OFDM Signal Generation and Wavelength Reuse for 1.25-Gbit/s Uplink Signal (OFC)

• W-band (100 GHz) hybrid access network design

W-Band Vector Signal Generation via Optical Millimeter-Wave Generation and Direct Modulation of NBUTC-PD (OFC, submitted to PTL)