Archived — Passive Components

>> Background History of Optical Circulator An optical circulator is a multi-port (minimum three ports) nonreciprocal passive component. The function of an optical circulator is similar to that of a microwave circulator—to transmit a lightwave from one port to the next sequential port with a maximum intensity, but at the same time to block any light transmission from one port to the previous port. Optical circulators are based on the nonreciprocal polarization rotation of the Faraday effect. Starting from the 1990s optical circulators has become one of the indispensable elements in advanced optical communication systems, especially WDM systems. The applications

>> The Birefringence of Single Mode Fiber Circular core fibers whose axes are straight are not birefringent – that is, the two orthogonally polarized LP01 mode have the same effective indices. Bending such a fiber introduces stresses in the fiber and makes the fiber linearly birefringent with the fast and slow axes in the plane and perpendicular to the plane of the loop, respectively. The bending-induced birefringence of a single mode silica fiber is given by: where nex and ney represent the effective indices of the LP01 modes polarized in the plane and perpendicular to the plane of the bend,

What is Fiber Bragg Grating – FBG A Fiber Bragg Grating FBG Device from JDSU Normal optical fibers are uniform along their lengths. In a simple fiber Bragg grating, the refractive index of the fiber core vary periodically along the length of the fiber, as shown in the following figure.   How Fiber Bragg Grating Reflects and Transmits Light As shown in the above figure, the refractive index of the fiber core is modulated with a period of Λ. When a light with a broad spectrum is launched into one end of fiber containing a fiber Bragg grating, the part

:: A Little Fiber Optic History Background 1965 – Charles Kao and George Hockham showed that if optical fiber’s attenuation can be reduced to less than 20dB/km, then it can be used as a transportation media for communication 1970 – Robert Maurer, Donald Keck, Peter Schultz, and Frank Zimar from Corning made a silica glass fiber with an attenuation of 17dB/km. 1977 – General Telephone and Electronics sent the first live telephone traffic through optical fiber, at 6 Mbit/s, in Long Beach, California. 1986 – David Payne and Emmanuel Desurvire invented EDFA (Erbium-Doped Fiber Amplifier) which eliminated the need for

>> Applications of Fiber Optic Coupler Fiber optic couplers are used to split the input signals into two or more outputs, they are called splitters in this case.  On the other hand, some types of couplers can be used to combine two or more inputs into one single output, they are called combiners in this case.   >> Fiber Optic Coupler Types 1. Y Coupler Y coupler is also called tap coupler. This type of coupler simply divides the signal into two outputs. The power distribution ratio between two outputs can be precisely controlled, such as 10/90 percent, 20/80 percent,