Method and arrangement to convert an optical data signal from a

Details Method and arrangement to convert an optical data signal from a Method and arrangement to convert an optical data signal from a

1993-10-28

1995-08-22

Noland, Thomas P.

Optical: systems and elements

Deflection using a moving element

Using a periodically moving element

359174, 359177, 375211, 375214, 455 9, H04B 1002

Patent

active

054445639

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a method and a device to convert an optical data signal from a multimode fibre to a corresponding signal which is transmitted further into a single mode fibre by means of a laser. In particular, the present invention relates to converting an incoming optical signal into electric signals which in turn are converted into an optical output signal. The incoming signal is generated by a light emitting diode meaning that it is optically incoherent. The outgoing signal is assumed to originate from a laser. The incoming optical data signal comprises "ones" (high optical level) and "zeros" (a lower optical level) and may also contain interruptions (a further lower optical level) and an overmodulated low frequency signal.


DESCRIPTION OF PRIOR ART

For many years it has been known that an incoming optical data signal may be recreated to a similar outgoing signal by having such signal go through a fibre optical regenerator which converts the incoming optical signal into electric signals, which in turn are converted into an optical output signal. In those instances where the type of incoming optical signal is known, i.e. such parameters as bit rate, encoding, etc. are known, it is possible to design an arrangement which recreates the incoming optical signal into a corresponding optical output signal. The drawback of such an arrangement is that if the optical input signal is different from the signal for which the arrangement was designed, it is likely that the conversion will not work. Further, with the exception of a data signal, there is no such arrangement known which manages to transfer an overmodulated low frequency signal and optical interruptions.
It should be noted that there are known fibre optical amplifiers which, without electric intermediary steps, may recreate an arbitrary optical input signal. Such fibre optical amplifiers require that the incoming optical signal be coherent. This is not a prerequisite of the present invention.


SUMMARY OF THE INVENTION

The technical problem of the present case is to be able to transfer a normal digital optical data signal, which additionally may contain optical interruptions, as well as an overmodulated low frequency signal, without detailed knowledge of the type of optical signal.
FIG. 1 demonstrates an example of such an optical signal. Note that the vertical scale is graded in dBm (dB related to I mW) to better manifest what a so called optical interruption implies. Due to practical reasons, FIG. 1 is not produced fully according to scale. If, for example, the data rate is 10 Mbit/s the overmodulated low frequency signal may only be of the order 5 Khz, i.e., several orders of magnitude less that the data rate, which is not obvious from FIG. 1. The optical interruption may typically vary from a few hundred .mu.s to several seconds.
In optical systems making use of interruptions, e.g., fibre optical network versions of a Token ring, Ethernet or Token bus, it is required that the optical power level, during the interruption, be very low, e.g., less than -40 dBm. Conventional laser transmitters are not able to transfer such interruptions since a laser transmitter is normally biased to its so called laser threshold, which may typically be at -25 dBm; i.e. about 30 times (15 dB) higher in power than an interruption. The present invention contains a laser transmitter which overcomes these concerns.
The most essential advantage of the present invention is that it is possible to transfer in a simple manner an unknown type of normal digital optical data signal which additionally may contain optical interruptions and an overmodulated low frequency signal.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph which demonstrates an example of an optical input signal and an optical output signal of the arrangement according to the present invention;
FIG. 2 is a block diagram which demonstrates an arrangement of the present invention;
FIG. 3 is an embodiment of a low pass filter 4 of the arrangement of FIG. 2;
FIG. 4 is

REFERENCES:
patent: 4257125 (1981-03-01), Theall, Jr.
patent: 4761797 (1988-08-01), Bickers
patent: 4864649 (1989-09-01), Tajima et al.
patent: 5162936 (1992-11-01), Taga et al.

Affiliated with

Also associated with

Rating

Method and arrangement to convert an optical data signal from a does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method and arrangement to convert an optical data signal from a , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and arrangement to convert an optical data signal from a will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2146071