FR2485837A1 - Single optical fibre line multichannel transmission system - uses superposition of different wavelengths or bands for subsequent separation by filtering - Google Patents

Abstract

The system utilises a red (1) and a green (2) light emitting diode which are coupled to a fibre optic cable (6) through a coupler (5). The diodes are biassed so that one is energised by positive pulses (2) while the other is energised by negative pulses (4). At a receiver, the cable is split into two, each part communicating respectively with a red filter (8) and green filter (9). The positive and negative signals are then recovered from the red and green light pulses using photoelectric generators suitably biassed. A wide band light source with a large number of colour or interference filters may be used to provide a large number of channels.

Description

a) The present invention relates to the use, on an optical fiber,
two or more infrared wavelengths, bright or
ultraviolet, each wavelength having its own pair of transmitters
and receivers, filters to avoid channel interference
on the other with the objective of increasing the capacities of the systems to
fiber optic transmission.

b) We know that the transmission of information, by giving this word the meaning
widest possible, on optical fibers takes more extension every day.

In fact, optical fibers are completely insensitive to radio interference. They allow extremely high transmission rates. Given their small dimensions and their ridiculous weight, they can achieve unsuspected performance with conventional electrical conductors.

Efforts to perfect this device have focused to date in the following directions - increase in the frequency of transmission, - decrease in the kilometric absorption of fibers, - increase in solidity, - etc ...

However, it must be recognized that, in return for many advantages, optical fiber transmitting light does not lend itself well to the transmission of certain signals, unlike electrical transmissions proper.

c) To cite just one example: an electrical signal can be transmitted in
the code "Manchester" by the signals llol '- 11+ 1 "and" - 1 ". In light, this
is unthinkable; you can only have two "no light" signals and
"presence of light".

The invention as it will be described overcomes this difficulty.

Likewise, it is a shame to be forced to use two different optical fibers if we want to simultaneously have information going from right to left and from left to right, on the same path.

Finally, despite the extremely high speeds which optical fibers already reach, these can be further improved by the application of the present invention.

d) Fiber optic transmissions always include a transmitter
light, ultraviolet or infra-red, the optical fiber and the receiver.

For obvious questions of performance, solidity and convenience of work, most transmissions are directed towards the use of LEDs in the near infrared whose efficiency is excellent and the switching speed high. They provide energy in a relatively narrow spectrum of wavelength on optical fibers whose absorption is minimal, in this same spectrum, associated with various receivers: PIN diode, for example, but nothing prevents, a priori, to choose another transmission mode
Green LED, yellow LED, laser, incandescent source modulated by a
Kerr, etc ...

It is therefore possible, more or less easily, to obtain sources
of different wavelengths, which require, for
work optimally, receptors sensitive to the same lengths
waves and also optical fibers whose absorption is reduced in
the spectrum considered. It is certain that from the idea that we are going
expose multiple progress can be made.

The present invention consists in sending, simultaneously, on the same fiber
as many messages as they are logical or analog as of bands
specialized spectral.

e) -We will specify on an example - see attached figure f) to transmit "Manchester" codes on a single optical fiber,
a LEflrouge (1) is actuated by the
positive pulses (2) of the code, a green LED (3) is activated by the
negative pulses (4) of the code Thanks to a conventional optical part (5),
the two elementary optical fibers connected to these two LEDs send the
message on a single optical fiber (6).

At the end of this fiber, another T (7) sends the message out of two
filters (8) and (9), the filter (8) allows only the red strip to pass
the filter (9) lets only the green strip of the LED (3) pass
Two receptors (10) and (11) then regenerate one of the positive signs of
initial signal, the other the negative signs.

g) But this example is not limiting, nothing prevents using a couple of
Green and red LED for example and a couple of receivers to transmit
speech in both directions simultaneously. This time we will have in us
referring to the figure; to the left of it: (1) and (11) and to the right
(10) and (3). But again, nothing prevents us from going further than using
of two spectral bands. Still using LEDs, you can, right now
nant, have three spectral bands easily achievable.

Nothing would also prevent the use of an incandescent source, whose spectrum
is extremely wide, cut into a large number of bands by filters
colored or interferential. On reception, the same filters as on transmission
again allowing to orient the signals in the useful bands.

The present invention according to the incessant progress of cells and
optical fibers can multiply transmission possibilities
of these fibers by a factor of 10, 100 or even 1000, in the near future.

Claims (4)

1.Thansmission bur a fiber optic beule of dibbénent logical bignaux characterized pan re bait that with each type of signal we abbect a wavelength or a band of optical wavelength (visible, infrared or ultra vioret). 2.Thansmission on a fiber optic beule of multiple logical or analog communications (murtiplexing), according to claim 1., carctenized pan bait that abbect to each communication a wavelength or an optical wavelength band. 3. Thansmission is a fiber optic beule, according to the preceding claims, characterized by the bimultaneous use of optical multiplexing and electrical multipeexing. 4. Thansmission bur a beule optical bibne of convensation in the two bens, belon the predecessor nevendications, canacténisée by the use of two wavelengths or two bands of wavelength abbect each to each direction.