Novel device concepts for optical WDM communications based on silicon etalons, fiber resonators and photonic bandgap fibers

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TKK dissertations, 145
Since the invention of the Erbium-doped fiber amplifier in 1987 and the preceding advances in low-loss single-mode fiber technology, fiber optic wavelength-division-multiplexing (WDM) has been the dominant technology of long-haul data transmission in the 1.55-mm region. Modern dense WDM (DWDM) systems can utilize more than 60 transmission channels in the C-band (1530-1570 nm) with a channel spacing of only 25 GHz. The combination of high modulation frequencies and small channel spacing place stringent requirements on the wavelength accuracy and long-term stability of the transmitting lasers. This Thesis presents simple inexpensive means for referencing and monitoring the channel wavelengths with wavelength references based on solid silicon Fabry-Perot resonators. The precise temperature control of the resonators enables both long-term stability for reproducible locking of lasers and fast sweeps to measure laser wavelengths. By employing unique pilot tones, the wavelengths and power levels of WDM channels can be directly measured from the optical multiplex of the transmission fiber. In photonic bandgap fibers, a class of photonic crystal fibers, most of the light intensity is guided in the air capillaries of the fiber. This provides the possibility to fill the capillaries with a gas, such as acetylene or methane, having suitable absorption bands coinciding with optical transmission frequencies. The Thesis presents practical applications utilizing these gas-filled fibers as miniature high-resolution absorption cells to provide references for calibrating secondary reference artifacts and measurement instruments. Moreover, multiple absorption lines of acetylene are shown to coincide with standardized DWDM transmission frequencies with adequate accuracy to be used as direct references for the transmission lasers. The second part of the Thesis deals with the development of novel all-optical and all-fiber components. The gas-filling techniques of photonic bandgap fibers are further exploited to fill a novel lead-glass photonic bandgap fiber with liquid crystal to construct a wideband thermo-optic switch. Also, a passive birefringent resonator made of a length of standard single-mode fiber with reflective end facets is demonstrated to be capable of multi-channel clock recovery in WDM applications where return-to-zero modulation is applied.
fiber optics, optical resonator, WDM, photonic crystal fiber, clock recovery
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  • [Publication 1]: Jesse Tuominen, Tapio Niemi, and Hanne Ludvigsen. 2003. Wavelength reference for optical telecommunications based on a temperature-tunable silicon etalon. Review of Scientific Instruments, volume 74, number 8, pages 3620-3623. © 2003 American Institute of Physics. By permission.
  • [Publication 2]: J. Tuominen, T. Niemi, H. Ludvigsen, M. Söderlund, and M. Leppihalme. 2004. Device for simultaneous monitoring of the channel wavelengths and power levels in a DWDM system. Journal of Optical Networking, volume 3, number 7, pages 501-509. © 2004 Optical Society of America (OSA). By permission.
  • [Publication 3]: J. Tuominen, T. Ritari, H. Ludvigsen, and J. C. Petersen. 2005. Gas filled photonic bandgap fibers as wavelength references. Optics Communications, volume 255, numbers 4-6, pages 272-277. © 2005 Elsevier Science. By permission.
  • [Publication 4]: T. Ritari, J. Tuominen, H. Ludvigsen, J. C. Petersen, T. Sørensen, T. P. Hansen, and H. R. Simonsen. 2004. Gas sensing using air-guiding photonic bandgap fibers. Optics Express, volume 12, number 17, pages 4080-4087. © 2004 Optical Society of America (OSA). By permission.
  • [Publication 5]: Jesse Tuominen, Hannu Hoffrén, and Hanne Ludvigsen. 2007. All-optical switch based on liquid-crystal infiltrated photonic bandgap fiber in transverse configuration. Journal of the European Optical Society - Rapid Publications, volume 2, 07016. © 2007 by authors.
  • [Publication 6]: Tuomo von Lerber, Jesse Tuominen, Hanne Ludvigsen, Seppo Honkanen, and Franko Kueppers. 2006. Multichannel and rate all-optical clock recovery. IEEE Photonics Technology Letters, volume 18, number 12, pages 1395-1397. © 2006 IEEE. By permission.
  • [Publication 7]: T. von Lerber, J. Tuominen, H. Ludvigsen, S. Honkanen, and F. Küppers. 2007. Investigation of multiwavelength clock recovery based on heterodyne beats of sideband-filtered signal. Optics Communications, volume 271, number 1, pages 87-90. © 2007 Elsevier Science. By permission.