Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
2001-11-27
2002-08-27
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200
Reexamination Certificate
active
06441937
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to an optoelectronic transceiver module having a coupling device for coupling at least one optical network through at least one optical waveguide, an optoelectronic transmitting apparatus that receives electrical data signals, converts them into optical data signals, and sends the signals through the coupling device to the optical network, and an optoelectronic receiving apparatus that receives the optical data signals passed through the coupling device from the optical network to the transceiver module and converts them into electrical data signals.
The invention also relates to a method for receiving optical signals having a first transceiver module with an optoelectronic transmitting and receiving device and a coupling device for coupling to an optical network. The optical data signals are sent from a second transceiver module through the optical network to the first transceiver module.
Such transceiver modules are normally used for bidirectional transmission of data in optical networks. If the transmitting apparatus in the transceiver (which, for example, has an LED or a laser) transmits optical signals, then a certain element of the signal is reflected on each optical boundary surface, which the signals strike on their path. Optical plug connections or optical boundary surfaces for inputting and outputting the light from and to a waveguide often have a completely unavoidable sudden change in the refractive index in the optical path of the light signals. Such a change necessarily leads to reflections.
It is disadvantageous if these reflections of the transmitted signals reach the receiving apparatus in the optoelectronic transceiver because they are superimposed on the received signals and, thus, corrupt the measurement result.
To insure that the bit error rate is at an acceptable level for the respective application despite the optical crosstalk, the detected, desired, received signals must be at a power level that is considerably greater than the power level of the undesirable reflected elements of the transmitted signals detected at the same time. Such a characteristic considerably reduces the limiting sensitivity of the transceiver.
One prior art technical solution to avoid the phenomenon is to use different optical carrier frequencies for the transmission and reception functions in the transceiver module. Frequency-selective components, for example, an optical filter, can be used to filter out the undesirable reflected elements of the transmitted frequency upstream of the receiving apparatus in a transceiver module. As such, the crosstalk can be reduced such that it is in the same order of magnitude as the attenuation of the frequency-selective optical component.
However, such a solution has the disadvantage that an additional optical component is required in the transceiver configuration. The additional component increases the production complexity and, thus, also results in higher transceiver costs.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide an optoelectronic transceiver module and a method for receiving optical signals that overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that allows the optical crosstalk of the transmitting apparatus in the transceiver module into the receiving apparatus to be suppressed as easily and effectively as possible without using a frequency-selective optical component.
With the foregoing and other objects in view, there is provided, in accordance with the invention, an optoelectronic transceiver module for coupling optical waveguides in an optical network having a specific reflection impulse response, including a coupler for coupling at least one optical waveguide of an optical network, the coupler having a given reflection impulse response, an optoelectronic transmitter receiving electrical data signals and converting the electrical data signals into optical data signals, the transmitter connected to the coupler for sending the optical data signals to the optical network, an optoelectronic receiver connected to the coupler for receiving the optical data signals from the optical network through the coupler and converting the optical data signals into electrical data signals, and an electronic compensator connected to the transmitter and to the receiver, the compensator generating an electrical correction signal using characteristic parameters of the reflection impulse response of the coupler and/or the reflection impulse response of the optical network and the electrical data signals received by the transmitter, the compensator correcting the electrical data signals received by the receiver using the electrical correction signal.
As such, the effect of optical pulses that the transmitting apparatus in a transceiver module transmits being partially reflected on boundary surfaces of the optical network and then being passed to the receiving apparatus in the transceiver module (which is, in itself, undesirable) is made use of to actively correct the data signals, which are received by the receiving apparatus, from the coupled optical network. The undesirable interference signal can, thus, be decoupled from the wanted signal, so that the limiting sensitivity of the receiving apparatus in the transceiver is considerably increased.
Furthermore, there is no longer any need for any additional optical components to prevent the undesirable crosstalk from the transmitted signals to the received signals in the same transceiver module. Accordingly, the transceiver module construction is simplified and the cost is reduced.
In accordance with another feature of the invention, the data signals, which are sent by the transmitting apparatus, are essentially at the same frequency as the data signals that are received by the receiving apparatus in the transceiver module. The compensation apparatus according to the invention in the transceiver module has the effect of eliminating the need to use different frequencies for bidirectional transmission by two transceiver modules. The different frequencies were required to allow the use of frequency-selective optical components to suppress the crosstalk from the transmission channel onto the reception channel. Thus, using essentially identical optical transmission and reception frequencies, there is no need to provide different transceiver modules, whose optical transmission and reception frequencies respectively had to be compatible with one another. A bidirectional optical data transmission path can, thus, be formed by two identical transceiver modules, which reduces the costs and considerably increases the flexibility for construction and conversion of such optical systems.
In accordance with a further feature of the invention, the optical data signals sent by the transmitter are light at a given wavelength and the optical data signals received by the receiver are light substantially at the given wavelength.
In accordance with an added feature of the invention, the compensation apparatus in the transceiver module advantageously determines the characteristic parameters of the reflection impulse response of the coupling device and/or of the optical network by transmitting defined test signals by the transmitting apparatus, with the receiving apparatus receiving the reflected elements of these test signals, resolved based on time and amplitude. Thus, the specific parameters of the optical system, which is coupled to the transmitting apparatus, can be determined in a sort of calibration measurement. To such an end, the compensation apparatus has an evaluation device that uses the amplitude ratio and the phase relationship between the transmitted test signals and the received reflection elements of these test signals to electronically determine the attenuation and phase angle of the reflected impulse response of the connected optical network. These two characteristic parameters make it possible to calculate the reflection impulse response
Baur Elmar
Hurt Hans
Wittl Josef
Greenberg Laurence A.
Mayback Gregory L.
Pascal Leslie
Singh Dalzid
Stemer Werner H.
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