DE19925408A1 - Optical signals dispersion compensator for optical data transmission - Google Patents

Abstract

A dispersion or propagation delay compensator includes an optical spectral filter equipped with a primary connection (6) and several secondary connections (7) at which part signals (TS1- TSn) of an optical signal are outputted. A circulator (1) is connected on the input-side of the spectral filter (5) and is used to pass an optical signal (OS) to the primary connection (6). Various delay lines (V1-Vn) are connected by their first connections to the secondary connections (7), and by their second connections - to a reflector (R1-Rn), so that the part-signals (TS1-TSn) are reflected and are assembled via the spectral filter (5) as a compensated optical signal (KS) and outputted at a further connection (4) of the circulator (1).

Description

Through dispersion - the frequency-dependent differences in transit time optical signals - becomes the one that can be bridged without regenerators Distance limited in optical data transmission. For Achieve greater ranges or to increase the Da it is necessary that the dispersion that occurs is compensated for as precisely as possible.

So far, dispersion-compensating fibers have been used frequently det, which has the same transmission properties as the over carrier fiber, however, have the opposite sign. To compensate for a certain transmission length is one matching length of the dispersion-compensating fiber not agile, d. H. an individual adjustment must be made. Despite this customization, a disper sions-compensating fiber due to manufacturing tolerances no optimal compensation can be achieved. Other disadvantages are the high attenuation, strong nonlinearity and considerable polarization dependent losses. This will make the performance ability of the transmission system despite the dispersion com pensions again severely restricted.

Compensation with fiber Bragg gratin has the disadvantage that optimal compensation only in a narrow wavelength gene range, for example in a channel of a wavelength multiplex systems, can take place or that a correspond fiber lattice reaches a length of over 2 m and then is very difficult to manufacture and at considerable costs.

Compensation by an optical FIR filter (Fi nite impulse response) is discussed theoretically, he but also seems problematic.  

The object of the invention is therefore a dispersion compen sator with relatively little effort. Another The task is to set the dispersion compensator to execute.

The main problem is caused by a dispersion compensator solved according to claim 1 or claim 2. Advantageous Next Formations of the invention are set out in the dependent claims ben.

In the solution specified in claim 1, it is advantageous that the delay lines from the Sig to be compensated nal are traversed back and forth, so only ge have shorter terms.

In contrast, the solution specified in claim 2 does not apply Circulator. The optical filters have to be very small Have pass bandwidths; but only a small one Selectivity is required, these filters can, for example wise with little effort as "Arrayed Waveguide Grating" be carried out.

It is particularly advantageous if the delay for the one individual partial signals can be changed, for example by the thermo-optical or the electro-optical effect (change delay due to temperature change or electri fields).

Embodiments of the invention are based on figures explained in more detail.

Show it:

Fig. 1 is a schematic diagram of a dispersion compensator,

Fig. 2 shows an adjustable dispersion compensator and

Fig. 3 shows a variant of the dispersion compensator.

Fig. 1 shows a dispersion compensator, the wesentli Chen from a circulator 1 , a spectral filter 5 , delay lines V ₁ to V _n and reflectors 9 ₁ to 9 _n and be. An applied at the input 2 of the circulator optical signal OS (wavelength division multiplex signal) is the primary input 6 of the spectral filter 5 is supplied. This filter splits the optical signal, for example a WDM signal, into numerous partial signals TS1 to TSn, which are emitted at the secondary outputs 7 ₁ to 7 _n . Delay lines V ₁ to V _{n are} connected to the secondary inputs and are preferably implemented by planar waveguides. Different materials such as glass, lithium niobate, aluminum oxide, plastics (polyamides) etc. can be used. At their second connection, the delay lines each have a reflector R ₁ to R _n . The dispersion of the individual spectral components is corrected by the different transit times (lengths) of the delay lines, the effect of the delay lines being used in the outward and return direction. This effect can be supported by the delay lines themselves having dispersion-compensating properties, ie wavelength-dependent transit times, so that an almost continuous dispersion function is achieved instead of a fine step function. So fewer delay lines are required. The reflected and compensated partial signals are summarized again by the spectral filter 5 and are outputted at the terminal 4 of the zirculator as a dispersion-compensated partial signal KS.

Fig. 2 shows a flexibly usable embodiment of the dispersion compensator, in which the delay times of the delay lines or a portion of them, as indicated by the hatched variable area VT, can be changed as individually as possible. This can compensate for tolerances or changes in the transmission properties of a transmission system.

In Fig. 3 a variant of the dispersion compensator is provided. The delay lines V ₁ to V _n are here between the first spectral filter 5 and a second spectral filter 10 through which the partial signals are combined again and output at the output 8 . As a result, the circulator can be dispensed with; however, a second spectral filter is required. With this variant, the delay times should be adjustable again.

Claims (6)

1. dispersion compensator,
characterized by
that an optical spectral filter ( 5 ) with a primary connection ( 6 ) and a plurality of secondary connections ( 7 ₁ to 7 _n ) is provided, at which partial signals (TS ₁ to TS _n ) of an optical signal are emitted,
that the spectral filter is connected upstream of (5), a circulator (1) via which an optical signal (OS) to the primary terminal (6) can be fed,
that to the secondary connections ( 7 ₁ to 7 _n ) with their first connections different delay powers (V ₁ to V _n ) are connected, to the second connections of which a reflector (R ₁ to R _n ) is connected so that the partial signals ( TS ₁ to TS _n ) reflected and via the spectral filter ( 5 ) summarized as a compensated optical signal (KS) to another connector ( 4 ) of the circulator ( 1 ). 2. dispersion compensator, characterized in
that an optical spectral filter ( 5 ) with a primary connection ( 6 ) and a plurality of secondary connections ( 7 ₁ to 7 _n ) is provided, so that an optical signal (OS) fed to the primary connection ( 6 ) receives a plurality of partial spectral signals (TS ₁ to TS _n ) is divided,
that to the secondary connections ( 7 ₁ to 7 _n ) different delay lines (V ₁ to V _n ) are each switched off with their first connections, the second connections of which are connected to inputs of a second spectral filter ( 8 ), at the output ( 9 ) of which the compensated optical signal (KS) is emitted. 3. Dispersion compensator according to A ₁ or A ₂ , characterized in that at least partially adjustable delay lines (VT; V1 to Vn) are provided. 4. Dispersion compensator according to one of the preceding claims, characterized in that spectral filters ( 5 ; 8 ) are hen with low selectivity. 5. Dispersion compensator according to one of the preceding claims, characterized in that the delay line (V ₁ to V _n ) has dispersion-compensating properties. 6. Dispersion compensator according to one of the preceding An claims, characterized, that as a delay line planar art waveguides substances is provided.