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Optics Express

Optics Express

  • Editor: Michael Duncan
  • Vol. 12, Iss. 4 — Feb. 23, 2004
  • pp: 651–656
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All-optical switching application based on optical nonlinearity of Yb3+ doped aluminosilicate glass fiber with a long-period fiber gratings pair

Yune Hyoun Kim, Nam Su Kim, Youngjoo Chung, Un-Chul Paek, and Won-Taek Han  »View Author Affiliations


Optics Express, Vol. 12, Issue 4, pp. 651-656 (2004)
http://dx.doi.org/10.1364/OPEX.12.000651


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Abstract

We propose a new fiber-type all-optical switching device based on the optical nonlinearity of Yb3+ doped fiber and a long-period fiber gratings(LPG) pair. The all-optical ON-OFF switching with the continuous wave laser signal at ~1556nm in the LPG pair including the 25.5cm long Yb3+ doped fiber was demonstrated up to ~200Hz upon pumping with the modulated square wave pulses at 976nm, where a full optical switching with the ~18dB extinction ratio was obtained at the launched pump power of ~35mW.

© 2004 Optical Society of America

1. Introduction

2. Experiments

A preform of high concentration Yb3+ doped aluminosilicate glass fibers for all-optical switching was fabricated by using the modified solution doping technique [8

8. J.S. Cho, U.-C. Paek, W.-T. Han, and J. Heo, “Fabrication and heat treatment effects on absorption characteristics of glass fibers doped with PbTe semiconductor quantum dots,” in Optical Fiber Communication Conference, Tech. Dig., Postconference ed., Vol. 54 of OSA Trends in Optics and Photonics (TOPS) (Optical Society of America, Washington, D.C., 2001), pp. ThC4-1–ThC4-3.

], in which the usual drain process was omitted, using an aqueous solution of YbCl3(0.05M) and AlCl3(0.24M) as a doping solution in the modified chemical vapor deposition(MCVD) process. The preform was drawn into fibers. The core diameter of the Yb3+ doped fiber, its absorption coefficient at the pumping wavelength of 976nm, and its cut-off wavelength were 4.4µm, 2.8cm-1, and 1.15µm, respectively. The concentration of ytterbium ions and aluminum ions in the fiber core was ~0.82at% and ~3.02at%, respectively, which were measured by the electron probe micro-analyzer(EPMA).

A LPG pair was written on the conventional single mode fiber(SMF) using the amplitude mask of 450µm period. Before writing the grating, the SMF was hydrogen loaded at 100°C under a pressure of 10 MPa for a week. After the grating formation on the bare fiber with the KrF excimer laser(248 nm), fibers were annealed at 100°C for 24 h. Then, the Yb3+ doped fiber was spliced between a pair of LPG as shown in Fig. 1(a). The total length, L, between the LPG pair including the Yb3+ doped fiber was 30.2cm, where the length, L1, of the Yb3+ doped fiber was 25.5cm. Because the LPG pair splicing with doped fibers is sensitive to the polarization of the incident light [9

9. Y.W. Lee, J. Jung, and B. Lee, “Polarization-sensitive interference spectrum o f long-period fiber grating pair separated by erbium-doped fiber,” IEEE Photon. Technol. Lett. 14, 1312–1314 (2002). [CrossRef]

], the polarization state from the continuous wave(CW) tunable laser source(TLS; TSL-200, Santec) was controlled to maximize the extinction ratio of the interference fringe pattern formed by the LPG pair with the Yb3+ doped fiber by using the polarization controller. Two 980nm/1550nm wavelength division multiplexers(WDM) were used to multiplex and demultiplex the pump beam at 976nm and the signal light near 1550nm, respectively. The interference fringes in the region of 1549–1559nm were monitored upon pumping at the launched pump power from 0 to ~56mW of a laser diode(LD; JDS Uniphase, at 976nm) by using the TLS and the power meter(81531A, Agilent), where the scanning interval of the TLS was 0.01nm.

All-optical ON-OFF switching experiment was carried out using the same LPG pair with the Yb3+ doped fiber as shown in Fig. 1(b). From the interference fringe pattern formed by the LPG pair with the Yb3+ doped fiber, a destructively interfered wavelength near 1550nm was chosen from the TLS. Then, the pump LD was modulated with a square wave pulse train, in which the lower power was 0mW and the upper power was the launched pump power corresponding to the ‘π’ phase shift. In order to examine the frequency dependence on the full optical switching (‘π’ phase shift), the modulation frequency of the pump signal from the LD driver was varied by using the function generator(33120A, Agilent). The TLS light signal after passing through the LPG pair including the Yb3+ doped fiber was detected at the 25GHz visible-infrared(400nm–1650nm) photo-detector(PD; New Focus) and the electrical signal from the PD was monitored in the oscilloscope(TDS220, Tektronix).

Fig. 1. Schematic diagram of experimental setup (a) for measuring the pump-induced phase change of the high concentration Yb3+ doped aluminosilicate optical fiber using a long-period fiber grating pair and (b) for all-optical ON-OFF switching at λ1 upon pumping with the square wave pulses at 976nm by varying the frequency.

3. Results and discussion

Δψ(λp)=2πλp0L1ΔncoreNLO(z)dz=2πsΔλ,
(1)

where ΔncoreNLO (z) is the effective refractive index change of the Yb3+ doped fiber core at z, λ p is the wavelength of the fringe, Δλ is the wavelength shift of λ p and s is the fringe spacing [4

4. Y.H. Kim, B.H. Lee, Y. Chung, U.C. Paek, and W.-T. Han, “Resonant optical nonlinearity measurement of Yb3+/Al3+ codoped optical fibers by use of a long-period fiber grating pair,” Opt. Lett. 27, 580–582 (2002). [CrossRef]

]. The phase change increased almost linearly with the pump power. The ‘π’ phase change corresponding to the full switching and the ‘1.53π’ phase change were obtained at the launched pump powers of ~35mW and ~56mW, respectively.

Fig. 2. (a) Transmission spectra at 1549–1559nm of the 25.5cm long Yb3+ doped optical fiber with the long-period fiber gratings pair upon pumping with the LD at 976nm. (b) Average wavelength shift at three destructively interfered wavelengths near 1550nm in (a) and its calculated phase shift with the launched pump power, where the error bars denote the maximum deviation of the shift.

Δf=12πτ.
(2)

If the carrier lifetime in the LED is regarded as the lifetime of the pumped energy level in the Yb3+ ions, the modulation bandwidth in the LPG pair including the Yb3+ doped fiber can be estimated to be ~212Hz, which is similar to the results shown in Fig. 3. Therefore, the all-optical switching performance shown in Fig. 3 is well explained by the radiative electronic transitions at the 2F5/2 energy level of the Yb3+ ions in the Yb3+ doped fiber.

On the other hand, Fig. 3(a) obtained from the 1Hz modulation showed a slightly additional increase and decrease in the TLS signal amplitude at the ON and OFF states, respectively, without spreading the pulses. The additional response is expected to be due to the thermal effect in the Yb3+ doped fiber since the thermal response time in Yb3+ doped alumino-germanosilicate fibers was reported to be ~150ms [11

11. M. Janos, J. Arkwright, and Z. Brodzeli, “Low power nonlinear response of Yb3+-doped optical fibre bragg gratings,” Electron. Lett. 33, 2150–2151 (1997). [CrossRef]

]. It is known that the doped fibers have a thermal effect due to the non-radiative electronic transitions in the dopant [3

3. M.K. Davis, M.J.F. Digonnet, and R.H. Pantell, “Thermal effects in doped fibers,” J. Lightwave Technol. 16, 1013–1023 (1998). [CrossRef]

]. The non-radiative transitions will be dissipated into a heat, which increases the temperature of the fiber. However, it was difficult to determine the thermal response time in our experimental results, which would be due to the small contribution of the thermal effect to the phase change in our method because of the one-fiber operation in principle [4

4. Y.H. Kim, B.H. Lee, Y. Chung, U.C. Paek, and W.-T. Han, “Resonant optical nonlinearity measurement of Yb3+/Al3+ codoped optical fibers by use of a long-period fiber grating pair,” Opt. Lett. 27, 580–582 (2002). [CrossRef]

]. Basically, the phase change in the LPG pair method is obtained by the change of the optical path difference between the core-guided light and the cladding-guided light of the fiber within the two same LPGs. If the temperature change of the core and the cladding in a single fiber between the LPG pair is the same, no phase change is expected. Since the temperature rise due to the pumping in the core and the cladding of doped fibers is about the same despite the different diameter and glass composition of the core and the cladding [3

3. M.K. Davis, M.J.F. Digonnet, and R.H. Pantell, “Thermal effects in doped fibers,” J. Lightwave Technol. 16, 1013–1023 (1998). [CrossRef]

], the thermal phase change in the LPG pair with the doped fiber would be negligibly small.

Fig. 3. All-optical ON-OFF switching results of the 1555.72nm CW light upon pumping at 976nm with the square wave pulses of (a) 1Hz, (b) 50Hz, (c) 100Hz, (d) 200Hz and (e) 250Hz using the function generator (Blue solid lines for the TLS signals, red solid lines for the pump signals and black solid lines for the function generator signals), where the blue dashed lines denote a zero transmission of the TLS signal.

Based on the thermal response time of ~150ms in the Yb3+ doped fiber, the thermal phase change in our experiments was estimated. The maximum modulation amplitude at 50Hz and 100Hz, where the thermal effect was averagely cancelled out, was ~94% compared to that at 1Hz, where the extinction ratio is expected to be ~18dB as in the case of the CW pumping. This means that the extinction ratio at 50Hz and 100Hz would be ~17.7dB. Also, the thermally induced phase change would be ~0.19rad in the ‘π’ phase change for the full optical switching. Note that the thermal effect of doped fibers on the phase change is different depending on the fiber device types, such as the fiber MZ interferometer, the TCF interferometer, the TMF interferometer and so on, and the thermally induced phase change in the ‘π’ phase change should be smaller than 0.2rad to keep the thermal phase bias change under -20dB [3

3. M.K. Davis, M.J.F. Digonnet, and R.H. Pantell, “Thermal effects in doped fibers,” J. Lightwave Technol. 16, 1013–1023 (1998). [CrossRef]

]. Therefore, the LPG pair with the doped fiber would have a negligible thermal effect and be a good candidate as an all-optical switching device.

4. Conclusion

The all-optical ON-OFF switching with the CW laser signal at ~1556nm was demonstrated by employing a long-period fiber gratings pair with the 25.5cm long Yb3+ doped aluminosilicate glass fiber(0.82at% Yb3+ and 3.02at% Al3+) upon pumping with the square wave pulses at 976nm by varying the frequency in the range of 1–250Hz, where the full optical switching with the ~18dB extinction ratio was obtained at the launched pump power of ~35mW. The switching extinction ratio, and the switching response time and pump power can be more improved by controlling the fabrication parameters of the LPG pair and inserting the higher nonlinear optical fiber with a faster response time, respectively. Also, it was found that the thermal effect of the LPG pair with the doped fiber would be small enough to be utilized in all-optical switching. Therefore, our proposed configuration by employing the LPG pair with the high nonlinear optical fiber will be useful as an all-optical switching device.

Acknowledgments

This work was partially supported by the Korea Science and Engineering Foundation through the Ultra-Fast Fiber Optics Networks Research Center, the Engineering Research Center program of the Kwangju Institute of Science and Technology, and by the BK-21 Information Technology Project, Ministry of Education, Korea.

References and links

1.

M. J. F. Digonnet, R. W. Sadowski, H. J. Shaw, and R. H. Pantell, “Resonantly enhanced nonlinearity in doped fibers for low-power all-optical switching: a review,” Optical Fiber Technol. 3, 44–64 (1997). [CrossRef]

2.

J. W. Arkwright, P. Elango, G. R. Atkins, T. Whitbread, and M. J. F. Digonnet, “Experimental and theoretical analysis of the resonant nonlinearity in ytterbium-doped fiber,” J. Lightwave Technol. 16, 798–806 (1998). [CrossRef]

3.

M.K. Davis, M.J.F. Digonnet, and R.H. Pantell, “Thermal effects in doped fibers,” J. Lightwave Technol. 16, 1013–1023 (1998). [CrossRef]

4.

Y.H. Kim, B.H. Lee, Y. Chung, U.C. Paek, and W.-T. Han, “Resonant optical nonlinearity measurement of Yb3+/Al3+ codoped optical fibers by use of a long-period fiber grating pair,” Opt. Lett. 27, 580–582 (2002). [CrossRef]

5.

N. S. Kim, S. Boo, Y.H. Kim, Y. Chung, and W.-T. Han, “Spectral characteristics of long period fiber grating pair using Yb3+ doped nonlinear optical fiber upon pumping,” in Proceedings of Conference on Optoelectronics and Optical Communications, (Optical Society of Korea, Gangchon, 2003), pp. 205–206.

6.

A.M. Vengsarkar, P.J. Lemaire, J.B. Judkins, V. Bhatia, T. Erdogan, and J.E. Sipe, “Long-period fiber gratings as band-rejection filters,” J. Lightwave Technol. 14, 58–65 (1996). [CrossRef]

7.

B.H. Lee and J. Nishii, “Dependence of fringe spacing on the grating separation in a long-period fiber grating pair,” Appl. Opt. 38, 3450–3459 (1999). [CrossRef]

8.

J.S. Cho, U.-C. Paek, W.-T. Han, and J. Heo, “Fabrication and heat treatment effects on absorption characteristics of glass fibers doped with PbTe semiconductor quantum dots,” in Optical Fiber Communication Conference, Tech. Dig., Postconference ed., Vol. 54 of OSA Trends in Optics and Photonics (TOPS) (Optical Society of America, Washington, D.C., 2001), pp. ThC4-1–ThC4-3.

9.

Y.W. Lee, J. Jung, and B. Lee, “Polarization-sensitive interference spectrum o f long-period fiber grating pair separated by erbium-doped fiber,” IEEE Photon. Technol. Lett. 14, 1312–1314 (2002). [CrossRef]

10.

T.P. Lee, C.A. Burrus JR., and R.H. Saul, “Light-emitting diodes for telecommunications,” in Optical fiber telecommunications II,S.E. Miller and I.P. Kaminow, eds. (Academic press, New York, 1988), pp.476–484.

11.

M. Janos, J. Arkwright, and Z. Brodzeli, “Low power nonlinear response of Yb3+-doped optical fibre bragg gratings,” Electron. Lett. 33, 2150–2151 (1997). [CrossRef]

OCIS Codes
(160.5690) Materials : Rare-earth-doped materials
(190.4370) Nonlinear optics : Nonlinear optics, fibers
(230.1150) Optical devices : All-optical devices
(230.4110) Optical devices : Modulators

ToC Category:
Research Papers

History
Original Manuscript: January 26, 2004
Revised Manuscript: February 11, 2004
Published: February 23, 2004

Citation
Yune Kim, Nam Kim, Youngjoo Chung, Un-Chul Paek, and Won-Taek Han, "All-optical switching application based on optical nonlinearity of Yb3+ doped aluminosilicate glass fiber with a long-period fiber gratings pair," Opt. Express 12, 651-656 (2004)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-12-4-651


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References

  1. M. J. F. Digonnet, R. W. Sadowski, H. J. Shaw, and R. H. Pantell, �??Resonantly enhanced nonlinearity in doped fibers for low-power all-optical switching: a review,�?? Optical Fiber Technol. 3, 44-64 (1997). [CrossRef]
  2. J. W. Arkwright, P. Elango, G. R. Atkins, T. Whitbread, and M. J. F. Digonnet, �??Experimental and theoretical analysis of the resonant nonlinearity in ytterbium-doped fiber,�?? J. Lightwave Technol. 16, 798- 806 (1998). [CrossRef]
  3. M.K. Davis, M.J.F. Digonnet, and R.H. Pantell, �??Thermal effects in doped fibers,�?? J. Lightwave Technol. 16, 1013-1023 (1998). [CrossRef]
  4. Y.H. Kim, B.H. Lee, Y. Chung, U.C. Paek, and W.-T. Han, �??Resonant optical nonlinearity measurement of Yb3+/Al3+ codoped optical fibers by use of a long-period fiber grating pair,�?? Opt. Lett. 27, 580-582 (2002). [CrossRef]
  5. N. S. Kim, S. Boo, Y.H. Kim, Y. Chung, and W.-T. Han, �??Spectral characteristics of long period fiber grating pair using Yb3+ doped nonlinear optical fiber upon pumping,�?? in Proceedings of Conference on Optoelectronics and Optical Communications, (Optical Society of Korea, Gangchon, 2003), pp. 205-206. [CrossRef]
  6. B.H. Lee and J. Nishii, �??Dependence of fringe spacing on the grating separation in a long-period fiber grating pair,�?? Appl. Opt. 38, 3450-3459 (1999). [CrossRef]
  7. J.S. Cho, U.-C. Paek, W.-T. Han, and J. Heo, �??Fabrication and heat treatment effects on absorption characteristics of glass fibers doped with PbTe semiconductor quantum dots,�?? in Optical Fiber Communication Conference, Tech. Dig., Postconference ed., Vol. 54 of OSA Trends in Optics and Photonics (TOPS) (Optical Society of America, Washington, D.C., 2001), pp. ThC4-1-ThC4-3.
  8. Y.W. Lee, J. Jung, and B. Lee, �??Polarization-sensitive interference spectrum of long-period fiber grating pair separated by erbium-doped fiber,�?? IEEE Photon. Technol. Lett. 14, 1312-1314 (2002). [CrossRef]
  9. T.P. Lee, C.A. Burrus, JR., R.H. Saul, �??Light-emitting diodes for telecommunications,�?? in Optical fiber telecommunications II, S.E. Miller and I.P. Kaminow, eds. (Academic press, New York, 1988), pp.476-484.
  10. M. Janos, J. Arkwright and Z. Brodzeli, �??Low power nonlinear response of Yb3+-doped optical fibre bragg gratings,�?? Electron. Lett. 33, 2150-2151 (1997). [CrossRef]
  11. A.M. Vengsarkar, P.J. Lemaire, J.B. Judkins, V. Bhatia, T. Erdogan, and J.E. Sipe, �??Long-period fiber gratings as band-rejection filters,�?? J. Lightwave Technol. 14, 58-65 (1996).

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