OSA's Digital Library

Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 16, Iss. 10 — May. 12, 2008
  • pp: 7447–7452
« Show journal navigation

Optically tunable multiband UWB pulse generation

Hongwei Chen, Tiliang Wang, Mo Li, Minghua Chen, and Shizhong Xie  »View Author Affiliations


Optics Express, Vol. 16, Issue 10, pp. 7447-7452 (2008)
http://dx.doi.org/10.1364/OE.16.007447


View Full Text Article

Acrobat PDF (150 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

A novel tunable multiband ultra-wide band (MB-UWB) pulses generation method using synchronously-apodized polarization modulation and birefringence time delay is proposed and demonstrated in this letter. Proper apodization profile is used to get MB-UWB pulses with spectra sidelobes suppression over 20dB. Five bands of MB-UWB pulses are generated by tuning the modulation frequency and transmitted over wireless channel. The central frequencies are from 4GHz to 6GHz and bandwidths larger than 500MHz. This method can be used in multiband modulation UWB over fiber systems.

© 2008 Optical Society of America

1. Introduction

Ultra-Wide-Band (UWB) is recently emerging as a solution for future wideband personal access networks (PANs) [1]–[2]

1. G. R. Aiello and G. D. Rogerson, “Ultra-wideband wireless systems,” IEEE Microw. Mag. 4, 36–47 (2003). [CrossRef]

. It has many advantages compared to traditional wireless communication technologies, such as low power consumption, high bit rate, immunity to multipath fading and so on [3]–[4]

3. D. Porcine, P. Research, and W. Hirt, “Ultra-wideband radio technology: Potential and challenges ahead,” IEEE Commun. Mag ,, 41, 66–74 (2003). [CrossRef]

. With the radio-over-fiber technology improvement, UWB over fiber can be a candidate solution for future wideband access networks with the advantage of low loss, high linearity, etc [5

5. Y. Kim, S. Kim, H. Jang, S. Hur, J. Lee, and J. Jeong, “Performance evaluation for UWB signal transmissions in the distributed multi-cell environment using ROF technology,” IEEE International Topical Meeting on Microwave Photonics, MWP’05.

]. So it’s greatly helpful to generate UWB pulses in optical domain. In UWB system, there are two main signaling formats, single-band and multi-band UWB (MB-UWB) waveforms. Compared to single-band UWB, multi-band UWB waveforms utilize overlapping groups of UWB signals such that each has a bandwidth of approximately 500MHz. This format ensures adherence to the FCC (The Federal Communications Commission) minimum bandwidth requirements and allows efficient utilization of the available spectrum [6

6. Fed. Commun. Commission, Revision of Part 15 of the Commission’s Rules Regarding Ultra-Wideband Transmission Systems, Apr. 2002. Tech. Rep., ET-Docket 98–153, FCC02-48.

]. Recently, there are many excellent schemes to be carried out to optically generate and distribute the monocycle and doublet pulses in single band [7]–[15]

7. W. P. Lin and J. Y. Chen, “Implementation of a new ultrawide-band impulse system,” IEEE Photon. Technol. Lett. 17, 2418–2420 (2005). [CrossRef]

, which show a good prospect for future UWB over fiber applications. However, up to now, there have been few attempts in generating MB-UWB pulse in optical domain.

In this letter, a simple method to optically generate MB-UWB pulses based on synchronous apodization and birefringence time delay is proposed and demonstrated. Electrical pulses are used to modulate optical signal so as to get polarity-reverse optical pulses pattern in orthogonal polarization orientation. The optical signal is then modulated with another apodization pulse and fed into a section of polarization-maintaining fiber (PMF). When the two polarity-reverse optical pulses are launched along two principle axes respectively, the birefringence time delay will help to generate the desired pulses. In experiment, we get five bands of MB-UWB pulses with different central frequency from 4GHz to 6GHz and a bandwidth larger than 500MHz.

2. Principle

Fig. 1. Principle of proposed scheme.

The proposed method is based on cross-polarization modulation and the main principle is shown in Fig. 1. The LiNbO3 phase modulator (PM) can be used as a polarization modulator as long as the input continuous-wave (CW) is launched at 45° relative to the principle axis. The main idea of polarization modulation and differential group delay (DGD) method is to generate a positive pulse in one polarization and a negative pulse in the other polarization by polarization modulation via RF pulses. The DGD stage redistributes this energy in time domain resulting in a time delay between the positive and negative pulses resulting in a monocycle pulse after O/E conversion since the photo detector only integrates the energy in time independent of polarization [16

16. H. Chen, M. Chen, and S. Xie, “PolSK Label Over VSB-CSRZ Payload Scheme in AOLS Network,” IEEE J. Lightwave Technol. 25, 1348–1355 (2007). [CrossRef]

].

The signal after first PM driven by a pulse train can be expressed as:

S1(t)=k=0MBk·P(t)·Eout·êout
(1)

where M is the bit length, Bk(t) is binary code of k-th bit, P(t) is one pulse shape and êout is the unit vector along the output electric field polarization. When P(t)=0, êout·êin=1, and êout·êin=0 when P(t)=Vπ. At this time, every pulse has identical amplitude. The output signals of PM1 are fed into second PM with same polarization orientation. PM2 is driven by an apodization pulse Ap(t) synchronized with driver signal of PM1. The input orientation of PM2 is kept the same as the output of PM1. When the cross polarization pulse train is fed into PM2, the apodization RF pulses are used to modulate them again. Due to the same principle as PM1, the output signal of PM2 can be expressed as:

S2(t)=k=0MAp(t)·Bk·P(t)·Eout·êout
(2)

Thus, after two cascaded phase modulators, the optical carrier is cross polarization modulated with apodized pulse train. If the driving bit pattern is “01” interleaved and after DGD component with time delay of one bit duration, the received signal can be expressed as:

S(t)=D0+Ap(t)×k=0N{P(t+2kT)P[t+(2k+1)T]}
(3)

where D 0 is direct current component, Ap(t) is apodization pulse shape, N is bit number of generated pulse pattern, T is bit duration and P(t) is one pulse shape in the pulse train. In Fig. 1, the final received signal can be seen as apodized monocycle pulse pattern with N=5. This kind of pulse has narrow bandwidth than single monocycle or doublet pulses and can be used in MB-UWB systems. The apodization pulse determines the pulse duration and shape of generated pulses. And this scheme has simple structure to realize.

3. Experiments and results

Experimental setup of our proposed scheme is shown in Fig. 2. The laser wavelength is 1550nm. Electrical pulses from pulse pattern generator (PPG: Advantest D3186) triggered with tunable microwave oscillator are used to drive an optical phase modulator (PM) and keep the peak-to-peak level to Vπ of PM. The linearly-polarized light is launched at 45° relative to the principal axis of PM. The driver electrical signal is fixed pattern of “1010101010101010101010101010101” (32 bits with “1” and “0” interleaved in 1024 bits period) with trigger frequency tunable from 8GHz to 12GHz. So the output of PM1 is orthogonal polarization pulse pattern with uniform amplitude. The second PM is driven by synchronous apodization pulse to adjust the amplitude profile of orthogonal pulse pattern. The trigger frequency of apodization pulse is 1/32 of microwave oscillator with bit pattern “01” interleaved. A low pass filter is placed after PPG2 with narrow bandwidth in order to reshape the apodization pulse. In fact, the signal out of PPG2 is square wave, and after low pass filter it will be reshaped to tailored pulse with gentle rising and falling edges. In the experiment, two filters are used with bandwidth of 300MHz and 200MHz to test performance of different apodization pulse shapes. The output orientation of PM2 is adjusted by a polarization controller (PC) and fed into a section of PMF with length of 90m after an EDFA. The beat length of PMF is 3.8mm and the time delay of two principle state of polarization (PSP) is about 120ps. After PMF, the optical signals are sent to the photo detector (PD) to become apodized monocycle pulse pattern. A wideband antenna is placed after PD without any electrical amplifier. And after wireless transmission, the UWB signal is received by another antenna and measured by a digital sampling oscillator (DSO, Tektronix TDS8200) and electrical spectrum analyzer (ESA, Agilent E4446A).

Fig. 2. Experimental Setup. DSO-digital sampling oscillator, EDFA-Erbium doped fiber amplifier, ESA-electrical spectrum analyser, FD-frequency divider, PC-polarization controller, PD-photo detector, PPG-pulse pattern generator, PM-phase modulator, PMF-polarization maintaining fiber.
Fig. 3. Spectra of monocycle pulse pattern with different apodization profiles.

First, we measured spectra of different apodized monocycle pulse patterns with trigger frequency of 12GHz. From Fig. 3, one can see that the monocycle pulses pattern without apodization has a peak at 6GHz in the spectrum with obvious low frequency part (from 1 to 4GHz) shown by dotted line. When 300MHz low pass filter is used, the monocycle pulse pattern is trapezium apodized with low frequency part suppressed over 5dB shown by dash line. And if 200MHz low pass filter is used, the apodization pulse is triangle-like, the final spectrum is quite well with greatly suppressed low frequency components shown by solid line in Fig. 2. The -10dB and -20dB bandwidths are 680MHz and 2GHz respectively which will cause little interference with adjacent channels in MB-UWB systems.

Secondly, with tunable microwave trigger source, different bands of MB-UWB pulses are generated and transmitted. We changed the trigger frequency from 8GHz to 12GHz and the low pass filter bandwidth is 200MHz. Figure 4 shows the time profiles of different frequency MB-UWB pulses before antenna and Fig. 5 shows the corresponding spectra. The generated MB-UWB pulses are all with tailored apodization. There are obvious rising and falling edges in pulse duration. From Fig. 5, one can see that five bands of MB-UWB are generated in FCC mask by tuning the trigger frequency. Bandwidth of each sub-band is larger than 500MHz which is in line with FCC definition. And the bandwidth is increasing with trigger frequency which is mainly because the pulse duration is shorter with higher frequency. The sidelobes are suppressed over 20dB for all sub-bands.

Fig. 4. MB-UWB pulses with different trigger frequency before wireless transmission.
Fig. 5. Normalized spectra of MBUWB bands with different trigger frequency before wireless transmission and FCC mask.

Fig. 6. MB-UWB pulses with different trigger frequency after wireless transmission.
Fig. 7. Normalized spectra of MB-UWB bands with different trigger frequency after wireless transmission and FCC mask.

Finally, this method can give us some useful discussions. This method is simple in principle and can be realized by integrated devices. The pulse train can be easily apodized by an apodization pulse triggered with frequency divider and shaped by filter or other devices. The center frequency and bandwidth of generated pulse is determined by trigger frequency and pulse duration respectively, which are pulse duration of P(t) and the number N in formula 3 as long as the modulator bandwidth is large enough. The sidelobe suppression is the contribution of apodization shape, which is Ap(t) in formula 3. So it’s easy and possible to tune the center frequency and bandwidth of sub-bands.

4. Conclusions

Acknowledgments

The authors would like to thank Dr. W.H. Chen for his help in providing the taper-slot antennas.

This work is supported by Tsinghua Basic Research Fund under Grant JC2007020, NSFC under Contract 60736002, National 863 Program of China under Contract 2007AA01Z264, National Basic Research Program of China (973 Program) under Contract 2006CB302806 and Open Fund of Key Laboratory of Optical Communication and Lightwave Technologies (Beijing University of Posts and Telecommunications), Ministry of Education, P. R. China.

References and links

1.

G. R. Aiello and G. D. Rogerson, “Ultra-wideband wireless systems,” IEEE Microw. Mag. 4, 36–47 (2003). [CrossRef]

2.

M. Z. Win and R. A. Scholtz, “Ultra-wide bandwidth time hopping spread spectrum impulse radio for wireless multiple-access communications,” IEEE Trans. Commun. 48, 679–689 (2000). [CrossRef]

3.

D. Porcine, P. Research, and W. Hirt, “Ultra-wideband radio technology: Potential and challenges ahead,” IEEE Commun. Mag ,, 41, 66–74 (2003). [CrossRef]

4.

M. Ghavami, L. B. Michael, and R. Kohno, Ultra wide-band signals and systems in Communication Engineering, (Wiley, West Sussex, England, 2004). [CrossRef]

5.

Y. Kim, S. Kim, H. Jang, S. Hur, J. Lee, and J. Jeong, “Performance evaluation for UWB signal transmissions in the distributed multi-cell environment using ROF technology,” IEEE International Topical Meeting on Microwave Photonics, MWP’05.

6.

Fed. Commun. Commission, Revision of Part 15 of the Commission’s Rules Regarding Ultra-Wideband Transmission Systems, Apr. 2002. Tech. Rep., ET-Docket 98–153, FCC02-48.

7.

W. P. Lin and J. Y. Chen, “Implementation of a new ultrawide-band impulse system,” IEEE Photon. Technol. Lett. 17, 2418–2420 (2005). [CrossRef]

8.

W. P. Lin and Y. C. Chen, “Design of a new optical impulse radio system for ultra-wideband wireless communications,” IEEE J. Sel. Top. Quantum Electron. 12, 882–887 (2006). [CrossRef]

9.

T. Kawanishi, T. Sakamoto, and M. Izutsu, “Ultra-wide-band radio signal generation using optical frequency-shift-keying technique,” IEEE Microw. Wirel. Compon. Lett. 15, 153–155 (2005). [CrossRef]

10.

F. Zeng, Q. Wang, and J. Yao, “An approach to all-optical UWB pulse generation,” IEEE International Topical Meeting on Microwave Photonics, MWP’06, P 13.

11.

F. Zeng and J. P. Yao, “An approach to ultra-wideband pulse generation and distribution over optical fiber,” IEEE Photon. Technol. Lett. 18, 823–825 (2006). [CrossRef]

12.

F. Zeng and J. P. Yao, “Ultrawideband signal generation using a high-speed electrooptic phase modulator and an FBG-based frequency discriminator,” IEEE Photon. Technol. Lett. , 18, 2062–2064 (2006). [CrossRef]

13.

Q. Wang, F. Zeng, S. Blais, and J. Yao, “Optical ultrawideband monocycle pulse generation based on cross-gain modulation in a semiconductor optical amplifier,” Opt. Lett. 31, 3083–3085 (2006). [CrossRef] [PubMed]

14.

F. Zeng, Q. Wang, and J. P. Yao, “All-optical UWB impulse generation based on cross phase modulation and frequency discrimination,” Electron. Lett. 43, 119–121 (2007). [CrossRef]

15.

H. Chen, M. Chen, C. Qiu, J. Zhang, and S. Xie, “UWB monocycle pulse generation by optical polarisation time delay method,” Electron. Lett. 43, 542–543 (2007). [CrossRef]

16.

H. Chen, M. Chen, and S. Xie, “PolSK Label Over VSB-CSRZ Payload Scheme in AOLS Network,” IEEE J. Lightwave Technol. 25, 1348–1355 (2007). [CrossRef]

OCIS Codes
(060.2330) Fiber optics and optical communications : Fiber optics communications
(060.5625) Fiber optics and optical communications : Radio frequency photonics

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: February 25, 2008
Revised Manuscript: April 1, 2008
Manuscript Accepted: May 7, 2008
Published: May 8, 2008

Citation
Hongwei Chen, Tiliang Wang, Mo Li, Minghua Chen, and Shizhong Xie, "Optically tunable multiband UWB pulse generation," Opt. Express 16, 7447-7452 (2008)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-10-7447


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. G. R. Aiello and G. D. Rogerson, "Ultra-wideband wireless systems," IEEE Microw. Mag. 4, 36-47 (2003). [CrossRef]
  2. M. Z. Win and R. A. Scholtz, "Ultra-wide bandwidth time hopping spread spectrum impulse radio for wireless multiple-access communications," IEEE Trans. Commun. 48, 679-689 (2000). [CrossRef]
  3. D. Porcine, P. Research, and W. Hirt, "Ultra-wideband radio technology: Potential and challenges ahead," IEEE Commun. Mag. 41, 66-74 (2003). [CrossRef]
  4. M. Ghavami, L. B. Michael, and R. Kohno, Ultra wide-band signals and systems in Communication Engineering, (Wiley, West Sussex, England, 2004). [CrossRef]
  5. Y. Kim, S. Kim, H. Jang S. Hur, J. Lee, and J. Jeong, "Performance evaluation for UWB signal transmissions in the distributed multi-cell environment using ROF technology," IEEE International Topical Meeting on Microwave Photonics, MWP�??05.
  6. Fed. Commun. Commission, Revision of Part 15 of the Commission�??s Rules Regarding Ultra-Wideband Transmission Systems, Apr. 2002. Tech. Rep., ET-Docket 98-153, FCC02-48.
  7. W. P. Lin and J. Y. Chen, "Implementation of a new ultrawide-band impulse system," IEEE Photon. Technol. Lett. 17, 2418-2420 (2005). [CrossRef]
  8. W. P. Lin and Y. C. Chen, "Design of a new optical impulse radio system for ultra-wideband wireless communications," IEEE J. Sel. Top. Quantum Electron. 12, 882-887 (2006). [CrossRef]
  9. T. Kawanishi, T. Sakamoto, and M. Izutsu, "Ultra-wide-band radio signal generation using optical frequency-shift-keying technique," IEEE Microw. Wirel. Compon. Lett. 15, 153-155 (2005). [CrossRef]
  10. F. Zeng, Q. Wang, and J. Yao, "An approach to all-optical UWB pulse generation," IEEE International Topical Meeting on Microwave Photonics, MWP�??06, P 13.
  11. F. Zeng and J. P. Yao, "An approach to ultra-wideband pulse generation and distribution over optical fiber," IEEE Photon. Technol. Lett. 18, 823-825 (2006). [CrossRef]
  12. F. Zeng and J. P. Yao, "Ultrawideband signal generation using a high-speed electrooptic phase modulator and an FBG-based frequency discriminator," IEEE Photon. Technol. Lett.  18, 2062-2064 (2006). [CrossRef]
  13. Q. Wang, F. Zeng, S. Blais, and J. Yao, "Optical ultrawideband monocycle pulse generation based on cross-gain modulation in a semiconductor optical amplifier," Opt. Lett. 31, 3083-3085 (2006). [CrossRef] [PubMed]
  14. F. Zeng, Q. Wang, and J. P. Yao, "All-optical UWB impulse generation based on cross phase modulation and frequency discrimination," Electron. Lett. 43, 119-121 (2007). [CrossRef]
  15. H. Chen, M. Chen, C. Qiu, J. Zhang, and S. Xie, "UWB monocycle pulse generation by optical polarisation time delay method," Electron. Lett. 43, 542-543 (2007). [CrossRef]
  16. H. Chen, M. Chen, and S. Xie, "PolSK Label Over VSB-CSRZ Payload Scheme in AOLS Network," J. Lightwave Technol. 25, 1348-1355 (2007). [CrossRef]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.


« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited