Fiber Optic Tutorials

This is a continuation from the previous tutorial - origins of chromatic dispersion.   Overview In the early 1990s, the deleterious effects of PMD were first reported in transmission of analog signals over Hybrid Fiber Coax (HFC) networks. The transmission distances in these networks were not long (typically <50 km), but the analog signals (unlike digital ones) were very sensitive to small levels of impairment that can be generated by unwanted dispersion. Here, it was found that chromatic dispersion, which is deterministic and can be compensated, was not the only impairment, but that PMD, coupled with source laser frequency chirp,...

This is a continuation from the previous tutorial - telephoto lenses.   Introduction An optical fiber’s dispersion is the tendency for the fiber to either broaden or  arrow a pulse as it travels along the fiber. The term chromatic dispersion is used to refer to the change in pulse shape that results when the velocity of the signal power along the fiber length is a function of optical frequency or wavelength. Chromatic dispersion alters the pulse shape because the signal power has a finite spectral width due to the spectral width of the signal modulation and the spectral width of...

This is a continuation from the previous tutorial - Petzval lenses.   A telephoto lens provides an effective focal length \(efl\) that is longer than its overall length \(s_{ol}\) as measured from the front of the lens to the image plane. The telephoto ratio is defined as \(s_{ol}/efl\), thus a lens with a ratio less than one is a telephoto lens. The basic concept of a telephoto lens is illustrated by the dialyte lens configuration in which a negative lens is inserted between the objective lens and the image plane. This concept goes back to Kepler, but Peter Barlow developed...

This is a continuation from the previous tutorial - double-Gauss lenses.   In 1839, Petzval designed a new type of lens that comprises a front objective with an achromatic, airspaced doublet as the rear elements. The Petzval lens has found great application in projectors and as a portrait lens. Both spherical aberration and coma can be well-corrected, but the lens configuration causes the Petzval sum to be undercorrected, which results in the field of view being limited by the astigmatism. The Petzval field curves inward and may be corrected by including a field flattener lens in close proximity to the...

This is a continuation from the previous tutorial - symmetrical lenses.   In the early 1800s, Gauss described a telescope objective comprising a pair of meniscus lenses with one having positive power and the other negative power. An interesting aspect of his lens is that the spherochromatism is essentially constant. Although this lens found little acceptance, in 1888, Alvan Clark of Massachusetts placed a pair of the Gauss lenses around a central stop to create a high-aperture, wide-field-of-view lens. This lens form is known as the Double-Gauss lens and is the basis of almost every high-aperture lens developed to date....