Fiber Optic Tutorials

This is a continuation from the previous tutorial - guided-wave all-optical modulators and switches. The word laser is an acronym for light amplification by stimulated emission of radiation. However, the term laser generally refers to a laser oscillator, which generates laser light without an input light wave. A device that amplifies a laser beam by stimulated emission is called a laser amplifier. Laser light is generally highly collimated with a very small divergence and highly coherent in time and space. It also has a relatively narrow spectral linewidth and a high intensity in comparison with light generated from ordinary sources....

This is a continuation from the previous tutorial - guided-wave optical frequency converters. As discussed in the (bulk medium) nonlinear optical modulators and switches tutorial, an all-optical modulator can be either of refractive type, which utilizes \(\boldsymbol{\chi}^{(3)'}\), or of absorptive type, which utilizes \(\boldsymbol{\chi}^{(3)''}\). For a guided-wave nonlinear optical device, however, any absorptive loss in the waveguide is detrimental to the device function due to the fact that the primary advantage of using an optical waveguide for the device is the long interaction length possible by the waveguiding effect. Therefore, all practical guided-wave all-optical modulators and switches are of refractive...

This is a continuation from the previous tutorial - nonlinear optical interactions in waveguides. All of the optical frequency converters discussed in the optical frequency converters tutorial can be made in waveguide structures. The basic principles and characteristics of these devices are the same as their bulk counterparts, except that the characteristics of the waveguide modes have to be considered. Though a guided-wave optical frequency converter generally takes the form of a single waveguide, there is often a possibility that multiple waveguide modes are involved in the frequency conversion process. Each individual frequency component can consist of multiple waveguide modes, as...

This is a continuation from the previous tutorial - Raman and Brillouin devices. As we have seen in the preceding tutorials, the efficiency of a nonlinear optical interaction generally increases with the intensities of the interacting optical waves and the interaction length. In a homogeneous bulk medium, the intensity of an optical wave can be increased by tightening the focus of the beam to reduce its cross-sectional spot size, but often at the expense of reducing the effective interaction length due to an increase in the beam divergence as a result of the decrease in the beam spot size. In...

This is a continuation from the previous tutorial - bistable optical devices. The nonparametric processes of stimulated Raman scattering and stimulated Brillouin scattering both cause a shift of the optical frequency, leading to a loss for the pump beam and a gain for a Stokes beam if the material is not originally excited or a gain for an anti-Stokes beam if it is excited. On the positive side, such processes can be utilized for optical frequency conversion and optical signal amplification. On the negative side, however, they also place some serious limitations on the performance of certain optical devices and...