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Unidirectional Optical Bus Network Using Doped Fiber Amplifiers

IP.com Disclosure Number: IPCOM000101556D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 3 page(s) / 105K

Publishing Venue

IBM

Related People

Liu, K: AUTHOR [+2]

Abstract

This article describes a novel passive optical bus network using distributed doped-fiber amplifiers with the following advantages. 1. Doped fiber amplifiers can be efficiently used in this network with only two pump sources, rather than a pump source for each piece of fiber. The pump efficiency can be maximized by proper design of the taps. The design minimizes the interference of the pump with the signal, so that the pump does not have to filtered out at each station before detection. 2. The use of amplifiers in the bus enables the number of stations to be increased by one to two orders of magnitude (1). 3. By judicious design of the amplifiers (essentially adjusting the length of doped fiber), the power from a particular transmitter to all the receivers can be made the same.

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Unidirectional Optical Bus Network Using Doped Fiber Amplifiers

       This article describes a novel passive optical bus
network using distributed doped-fiber amplifiers with the following
advantages.
1.   Doped fiber amplifiers can be efficiently used in this network
with only two pump sources, rather than a pump source for each piece
of fiber.  The pump efficiency can be maximized by proper design of
the taps.  The design minimizes the interference of the pump with the
signal, so that the pump does not have to filtered out at each
station before detection.
2.   The use of amplifiers in the bus enables the number of stations
to be increased by one to two orders of magnitude (1).
3.   By judicious design of the amplifiers (essentially adjusting the
length of doped fiber), the power from a particular transmitter to
all the receivers can be made the same.  This makes the dynamic range
of all the receivers identical, allowing the same part number to be
used.

      The bus topology is commonly used in electrical computer
networks because the natural ordering of stations along the bus
permits a number of efficient protocols to be used.  In an all
optical network, the bus topology is not very desirable (2) because
the splitting and excess losses at the passive optical taps restrict
the number of stations to a few tens typically.  The use of optical
amplifiers, however, rejuvenates this topology because these
amplifiers can be used to compensate for the tap losses.  One
particularly attractive implementation uses doped fiber amplifiers
which can easily give distributed gain.

      A doped fiber amplifier (3) consists of a length of fiber doped
with ions.  A popular formula for amplification at 1.55 microns is a
combination of erbium and aluminum ions.  The amplifier is pumped
using an optical pump source. Because the amplifier fiber is spliced
to normal system fiber, it is relatively simple to add multiple fiber
amplifiers to a system. Since the sections of amplifier fiber may be
interspersed with sections of normal fiber, a single pump source may
power multiple amplifiers.  In contrast, semiconductor amplifiers are
much more difficult to splice into systems and need to be powered
independently. Therefore, fiber amplifiers are particularly
attractive for applications where multiple stages of low g...