EP2156578A1 - Liaison optique - Google Patents

Liaison optique

Info

Publication number
EP2156578A1
EP2156578A1 EP08767064A EP08767064A EP2156578A1 EP 2156578 A1 EP2156578 A1 EP 2156578A1 EP 08767064 A EP08767064 A EP 08767064A EP 08767064 A EP08767064 A EP 08767064A EP 2156578 A1 EP2156578 A1 EP 2156578A1
Authority
EP
European Patent Office
Prior art keywords
electrical
optical
link
cable
signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP08767064A
Other languages
German (de)
English (en)
Other versions
EP2156578A4 (fr
Inventor
Hjalmar Hesselbom
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
InvOpto AB
Original Assignee
InvOpto AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by InvOpto AB filed Critical InvOpto AB
Publication of EP2156578A1 publication Critical patent/EP2156578A1/fr
Publication of EP2156578A4 publication Critical patent/EP2156578A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2589—Bidirectional transmission

Definitions

  • the present invention relates to a basically electrical transmission link having a portion thereof designed as an optical link or/and a optical only transmission link using electrical protocols and signaling (electrical PHY-circuits).
  • a bidirectional link using a standard twisted pair (TP) cable for transmission of electrical digital signals is illustrated in Fig. 2a.
  • the electrical signals at the ends of the transmission link are input to/output from end equipments 1 connected at the ends of the twisted pair cable 3.
  • the twisted pair cable contains at least two wire pairs 5, one pair for each direction.
  • Each of the end equipments 1 includes a transmitter circuit (TX) 7 and a receiver circuit (RX) 9.
  • the transmitter and receiver circuits can generally contain pulse transformers, not shown, for providing the balanced electrical signal output to the wire pair used for transmission from the respective end equipment and for receiving the balanced electrical signal that has propagated through the another wire pair of the TP cable 3.
  • the electrical signals received from the TP cable and received by the respective RX 9 have undergone some distortion but still the original digital signal can be detected using e.g. a simple receiving circuit including a pulse transformer and possibly a smoothing inductor.
  • the balanced electrical signals that have propagated through the TP cable 3 have been more distorted, the distortion e.g. including a frequency dependent attenuation as seen in the diagram of Fig. 1.
  • an additional active receiver circuit 11 is required in the end equipment 1, the active receiver circuit receiving the electric signal from the RX 9 in the end equipment and providing the electrical digital signal output from the end equipment that agrees with the electrical digital signal provided to the end equipment at the other end of the TP cable 3.
  • the active receiver circuit includes, as seen in Fig. 2b, a dynamic equalizer 13 and a bit detector 15.
  • the dynamic equalizer can basically include an amplifier that has a frequency dependent characteristic allowing that from the unbalanced electrical signal detected by the RX 9 a signal is output that is sufficiently similar to original electrical signal input from the end equipment into the TP cable at the other end of the TP cable 3 to allow a detection of the bit content of the signal by the bit detector 15.
  • the dynamic equalizer can have an amplification characteristic, see Fig. 3, that corresponds to the inverted frequency characteristic of the TP cable length seen in Fig. 1.
  • the active receiver 11 can include other functions such as a circuit for switching between receiving a 10 Mbit/s signal and a 100 Mbits/s signal, not shown, and a selector circuit 17 for detecting an equivalent length of the wire pair 5 used for the transmission and setting the frequency dependent characteristic of the dynamic equalizer 13 accordingly.
  • the most common TP cable presently used is the Cat (category) 5 TP cable that allows, according to the ANSI/EIA (American National Standards histitute/Electronic Industries Association) Standard 568, a maximum data rate of 100 Mb/s and usual applications include 100 Mb/s TPDDI and 155 Mb/s ATM. It often holds four twisted pairs, two pairs used for one bidirectional communication channel and the other two pairs being unused or possibly used for another bidirectional communication channel, compare Fig. 2a. It is generally used for twisted pair signaling according to the 100BASE-TX Fast Ethernet standard, is the cable most frequently used in LANs and has nowadays actually replaced the older 1 OBASE-T and 10BASE-2 (coaxial) cables. Signaling and connectors according to the 100BASE-TX standard follow the same wiring patterns as those for 1 OBASE-T.
  • a middle part of the transmission link can be an optical fiber or a pair of optical fibers, see Fig. 2c, where only the components necessary for transmission in one direction are shown.
  • a first part of the transmission link can then be a TP transmission link 21 of the kind illustrated in Fig. 2a, a second part a fiber optical link 23 including an electrical-to-optical converter 25 at the input end of the optical fiber 35 and an optical-to-electrical converter 29 at the opposite, output of the optical fiber, and a third part 43 another TP transmission link.
  • Equipment performing conversion tasks for converting signals between different media can generally be called media converters.
  • Conventional such equipment for communication according to the Ethernet standard and converting between signals propagating in a TP cable and an optical fiber contain, for one communication direction, complete TP termination including equalization, clock recovery, bit detection, descrambling, 5b to 4b conversion and serial to parallel conversion on the electrical side followed by parallel to serial conversion, 4b to 5b encoding and optical transmission on the optical side and in the opposite communication direction optical to electrical conversion, clock recovery, bit detection, 5b to 4b decoding and serial to parallel conversion on the optical side followed by parallel to serial conversion, 4b to 5b encoding, scrambling and electrical transmission on the electrical side, see Fig. 2d.
  • a proximate portion of the link such as at a central switch
  • the .distant portion such as at end equipment
  • the TP cable lengths can be connected at both ends of the optical fiber segment.
  • a 100 Mb/s signal according to the 100BASE-TX Fast Ethernet standard is noticeably distorted even after having propagated over only a short length of cable due to frequency dependent attenuation as shown for different cable lengths in the diagram of Fig 1.5
  • Applying such a signal to an optical transmitter modulating the light in an analog fashion and then receiving it using a (dual) comparator (due to the 3-level signal), as suggested in the cited patent application creates a signal from the dual comparator that in most cases is quite different from the signal entering the optical transmitter but also strongly distorted relative to the original 3-level signal entering the twisted pair cable preceding the optical transmitter, due to a more or0 less severe phase distortion and even loss of detectable bits introduced by primarily the combination of fixed trigger levels of the dual comparator and the inter symbol interference on the signal received on the fiber replicating the signal originally on the TP cable end at the electrical to optical converter.
  • a 100 Mb/s receiver that is adapted to the 100BASE-TX Ethernet standard mentioned above is designed to be capable of interpreting signals that have passed a Cat 5 TP cable having a length, from 0 to 100 m.
  • the signal received after 100 m is heavily distorted compared to the 3- level digital signal entering the TP cable as the higher frequency components are much more attenuated than the lower frequency components, this resulting in severe inter symbol modulation
  • the attenuation in dB increases with the square root of the frequency and linearly, also in dB, with the length of the cable or rather, the attenuation in dB/m increases with the square root of the frequency at least for frequencies over 1 MHz and up to well above 100 MHz as illustrated in Fig. 1.
  • a 100 Mb/s TX signal according to the Ethernet standard specification mentioned above is a differential three-level signal coded such that every new 1 in the sequence changes the state of the output in the sequence 0 V, +V, 0 V, -V, 0 V, etc., whereas every new 0 in the sequence does not change the state..
  • the effective physical band width is reduced by a factor of two. Due to the 4b to 5b coding performed before transmitting to avoid long periods of successive ones or zeroes the signal is transmitted at 125 Mb/s.
  • the highest fundamental physical frequency for any bit sequence without the three level coding would be 62.5 MHz, but due to the three level coding (MLT-3) it is reduced to 31.25 MHz.
  • the third harmonic at 93.75 MHz should not be reduced more than a few dB.
  • this frequency has been reduced by approximately 9 dB in relation to the fundamental frequency and it has been reduced by 20 dB in relation to the lowest used frequency.
  • This 20 dB relative reduction is compensated for by the dynamic equalizer at the receiver before bit detection.
  • the idle signal used in order to phase lock the clock retrieval and for link integrity purposes in the bit detector 11, also contains symbols up to 12 bits long which also need to be transmitted. This is equivalent to a physical frequency of approximately 2.5 MHz.
  • a 100 Mb/s optical signal according to the 100BASE-FX Ethernet standard or the Ethernet standard 802.3u using the ANSI X3T9.5 FDDI Physical Layer Dependent (fiber PMD) standard is also 4b to 5b coded resulting in a line bit rate of 125 Mb/s. This is however a usual NRZ signal and thus the highest physical fundamental frequency is 62.5 MHz.
  • the third harmonic in this case 187.5 MHz, can be reduced by more than several dB, but the detectability (the "openness of the eye") would be increased if this harmonic was not reduced by more than 7 dB.
  • an optical receiver has no dynamic equalizer, as an optical fiber does not impose any frequency dependent attenuation. Instead, an optical receiver usually has an automatic gain control (AGC) function that compensates for variable frequency independent losses due to different lengths of optical fiber and different numbers of connections/connectors in the transmission path.
  • AGC automatic gain control
  • optical link as described herein provides a solution for allowing significant further distortion of the electrical signal from point where it enters the first converter (converting from electrical to optical signaling) to the point where it exits from the second converter (converting from optical to electrical signaling).
  • an optical link includes an optical fiber for transmission of signals and has from an electrical input terminal to an electrical output terminal a frequency dependent loss and phase linearity characteristics that are equal or similar, for at least a particular or predetermined frequency region, to a specific length of an electrical cable such as a twisted pair cable regardless of the actual length of the optical fiber, naturally within certain but wide limits.
  • the optical link may for this purpose include specially selected components or compensating devices such as filters or other devices configured in a suitable way.
  • Fig. 1 is a diagram showing graphs of frequency dependent loss for a 30 m and a 60 m long Cat 5 TP cable (one pair),
  • - Fig. 2a is a schematic of a complete twisted pair link according to the 100BASE-TX standard
  • - Fig. 2b is a schematic of the receiver portion of end equipment used for terminating communication over a twisted pair cable according to the 100BASE-TX standard
  • - Fig. 2c is a schematic of a composite communication link for one-directional transmission having an extended total length using an optical portion e.g. according to U.S. patent 4,691,386,
  • - Fig. 2d is a schematic of a composite communication link for one-directional transmission having an extended total length, where TP end equipment and fiber end equipment are integrated to form media converters
  • - Figs. 2e and 2f are schematics of a composite communication link for one-directional transmission having an extended total length, the optical portion using direct converters according to the published International patent application WO 02/23771,
  • - Fig. 2g is a schematic of a composite communication link for one-directional transmission having an extended total length using an ideal analog optical link
  • - Fig. 2h is similar to Fig. 2g of a composite communication link for one-directional transmission including non-ideal components and possibly a correcting circuit
  • - Fig. 2i is a schematic of an optical link where the direct converting converters are directly, without using any length of TP cable, connected to TP end equipment including TP PHY circuitry for detection of signals
  • - Fig. 3 is similar to Fig. 1 showing graphs of the characteristics of an equalizer function in the receiving portion of end equipment
  • - Figs. 4a and 4b are schematics of optical-to-electrical conversion circuits having an AGC- function
  • - Fig. 5 is a diagram where the graphs A and B represent the frequency characteristics (attenuation) of 30 m and 60 m Cat 5 TP cables, respectively
  • C and D represent the frequency characteristics of non ideal optical links having a first order low pass characteristic for emulating frequency characteristics within the required frequency range for TP cables of 30 m and 60 m lengths, respectively
  • Fig. 6 is similar to Fig. 5 but for a logarithmic frequency scale
  • Fig. 7 is a diagram of a correcting circuit
  • - Fig. 8 is a diagram of graphs of the characteristic of the correcting circuit of Fig. 7 and of ideal characteristics and the difference between them
  • - Fig. 9 is a diagram of graphs of the frequency dependence of a signal having passed a non-ideal optical link and of a signal having passed a TP cable, and the correction characteristics and the resulting characteristics after applying the correction
  • - Fig. 10 is a graph of the group delay as a function of frequency caused by the correcting circuit of Fig. 7, - Fig. 1 Ia is a schematic of a complete unit for direct electrical-to-optical conversion, and
  • FIG. 1 Ib is a schematic of a complete unit for direct optical-to-electrical conversion.
  • End equipment for terminating communication over a twisted pair cable according to the
  • 100BASE-TX standard has built-in facilities for receiving twisted pair signals that are designed to be capable of compensating for the signal distortion appearing after propagating through a Cat
  • Fig. 2b In the schematic of Fig. 2b conventional components at the end of a twisted pair cable 3 for digital transmission at 100 Mb/s are illustrated.
  • the receiver 9 receives the electrical signals through a connector 31 from one wire pair 5 of the cable.
  • the received signals are input to a dynamic equalizer 13 compensating for the frequency dependent loss of the cable 3 to render an undistorted signal or at least a signal that sufficiently agrees with the electrical signal input to the cable.
  • the term "dynamic" implies that the compensation is adjusted according to Fig. 3 to the correct length of TP cable used. Choosing the correct amount of compensation is done in many ways, e.g.
  • the dynamic equalizer 13 may apply a frequency dependent amplification to the received signal.
  • the graphs of Fig. 3 are amplification characteristics that are appropriate for a 30 meter and a 60 meter long Cat 5 TP cable, respectively. Obviously, such amplification characteristics are substantially .the opposite to the characteristic of the frequency dependent attenuation of the used cable length.
  • the signal from the dynamic equalizer 13 is provided to a bit detector 15 from which the obtained digital signal is output to other devices, not shown, for further processing or use.
  • a portion of such a transmission link can be replaced by an optical link including optical fibers.
  • directly converting analog converters 33 can be used on either side of a piece of optical fiber 35, as illustrated in Fig. 2g.
  • the addition of the optical link segment is, using an ideal analog optical link, not seen from the electrical signal point of view and hence the total added length of the two TP cables, only one wire pair 5', 5" thereof shown in Fig. 2g, is maximally 100 m, this length being arbitrarily divided between the two TP cable parts.
  • the system would however see a further delay which is of no concern using full duplex which is anyway required when electrical or optical links having a delay more than that of a 100 m TP Cat 5 cable are used.
  • a typical installation based on TP cables may include a switch, not shown, that is connected to a converter pair via a patch cable of the twisted pair type having a length up to 2 m.
  • the optical fiber is at one end connected to such a converter pair and at the other end another converter pair is attached which is connected to user equipment via a TP cable having a length less than 30 m.
  • an optical analog link in which the electrical signal is directly converted to optical form and back as described above and where the converters themselves have no conventional receivers or transmitters for communication according to the 100BASE-TX standard, between the TP cable ends, in this example, does not require a frequency dependent attenuation better than that of a 68 m long TP cable, i.e. it can have a frequency dependent attenuation smaller than or equal to that of a 68 m long TP cable and the combined transmission -link will still work.
  • the optical link portion can have the same frequency and phase linearity characteristics as a 68 m long Cat 5 TP cable and will hence behave as a 68 m long Cat 5 TP cable in the total transmission link, and when connected to a total of 32 m long Cat 5 TP cable arbitrarily divided between the two ends of the optical portion, the total transmission link will work as a 100 m long Cat 5 TP cable.
  • an optical link having the same frequency and phase linearity characteristics as a 30 m long Cat 5 TP cable will work as a 30 m long Cat 5 TP cable allowing for up to a total of 70 m Cat 5 TP cable to be arbitrarily divided between the two ends, and so on.
  • the output amplitude within the used physical bandwidth should be independent of the optical (frequency independent) loss/fiber length. This can be achieved in two different ways, or as a combination of these two different ways, depending on the sensitivity to the absolute level of (the lowest frequency component of) the signal of the dynamic equalizer in the end equipment.
  • an AGC function keeping the amplitude of (the lowest frequency component of) the output signal into the TP cable to a set value within the specified input range of the TP receiver, usually an amplitude in the range of 0.5 - 1 V, independent of the fiber loss is sufficient. This is the case for many TP Ethernet receivers of today.
  • the AGC would not be dependent on the amplitude of the signal (the light modulation) but on the average optical signal, i.e.
  • a non-ideal optical link including e.g. non- ideal analog converters 39 for converting between electrical and optical signals, these converters e.g. having a reduced band-width, compare the discussion above.
  • a compensator 41 may be included at the end of the optical link to restore the signal to be sufficiently similar to a TP signal.
  • FL max designates the maximum fiber length for which the AGC- of the optical receivers can compensate, see the discussion herein, and/or where other phenomena like path length or wave length dispersion limits the maximum fiber length.
  • L max is the maximum length of TP cable for which the equalizers in the TP receivers of the end equipment for 100Base-TX communication can compensate and L e q is the length of the TP cable that the optical link emulates.
  • a total of up to L max - L e q can be arbitrarily divided between the left and the right TP cables.
  • the end equipment TP receivers are now aware of the inclusion of the optical link, but interprets this as an added length (equal to L eq ) of TP cable for which the equalizers can compensate.
  • both the transmitter and the receiver should have an approx. -7 dB bandwidth of 187 MHz.
  • a link as described herein, however, corresponding to a 60 m long Cat 5 TP cable needs a 95 MHz transmission roughly 6 dB below the 32 MHz signal level which can be 5.5 dB below the 2.55 MHz (corresponding to the longest symbol of the idle signal) signal level, i.e. the signal at 95 MHz can be roughly 11.5 dB attenuated relative the lowest used frequency.
  • a frequency and possibly phase characteristics compensation network as generally seen in e.g. Fig. 1 Ib is required to more or less equate the frequency and phase linearity characteristic to that of a Cat 5 TP cable between 2.5 MHz and 95 MHz, as for this kind of signal, there is substantially no necessary information above 95 MHz. Therefore this compensation network only has to work between the lowest used frequency, in this case approx. 2.5 MHz, and the highest used frequency, 95 MHz. This can in principle be accomplished using simple passive components. Depending on the specific properties of different PHY circuits, varying degrees of non perfect frequency and phase linearity characteristics the correction/simulation will still work.
  • a compensating circuit working as a simple correction filter is seen in Fig. 7. It has been designed to convert a signal that has passed a non-ideal optical link of limited bandwidth working as a first order low pass filter, which e.g. can be assumed to have the same attenuation at 100 MHz as a 60 m Cat 5 TP cable, to become more similar, over the whole frequency range used, to a signal which has passed a real Cat 5 TP cable of the equivalent length.
  • a graph of the characteristic of the filter is shown in Fig. 8.
  • the characteristic A of the correcting filter of Fig. 7 is close to the characteristic B of an ideal correction circuit line.
  • the deviation from the ideal characteristic seen at C is only significant for frequencies lower than those used according to the 100BASE-TX standard and for third harmonics where for the highest at 93.75 MHz a reduction of a few dB is fully acceptable.
  • Fig. 9 other graphs of the correcting operation are shown.
  • the correction filter according to Fig. 7 has the characteristic seen at A.
  • the resulting signals After it has been applied to signals that have passed an uncorrected, non-ideal optical link which should emulate a 60 m Cat 5 TP cable and which is assumed to have the characteristic seen at B, the resulting signals has an overall characteristic C that is very similar to the characteristic D of a 60 m Cat 5 TP cable.
  • a general uncorrected link characteristic being that of a first order low pass filter is here only given as a simplified example to show the principle of converting a particular characteristic to that of a specific length cable.
  • Figs. 11a and l ib showing the complete converter units for the direct conversion between electrical and optical signals, there are at least three amplifiers and some other components, each having their own frequency characteristic, for signals passing the optical link.
  • the total uncorrected link characteristics are more complicated than those of a first order low pass filter. Therefore, the specific correction filter needed will be designed after having determined the virgin characteristics of the optical link to be corrected. Because the optical link consists of at least three amplifiers, the correction filter does not have to be connected at one single location.
  • partial corrections may be performed either directly preceding or directly succeeding or as part of the local feedback loop of each amplifier utilizing their respective relatively high input impedance and/or low output impedance for easy filter design without having to use extra amplifiers. For example if the voltage amplifier in the AGC and cable driver stage has a too low -3 dB point, this may be compensated by modifying the negative feed back of that stage to include a low pass characteristic with a properly chosen -3 dB point.
  • the corrected link including the correction filter must be sufficiently phase linear or have a sufficiently constant, frequency independent group delay within the frequency range used for the signaling system.
  • the value of this constant delay is arbitrary as long as full duplex is used.
  • group delay variation should be less than a fraction of the period of the highest frequency used for all frequencies. Not fulfilling this will cause signal distortion which would still allow correct detection but would "close the eye” in the eye diagram causing an increased bit error ratio (BER).
  • the amplifiers illustrated in the generic drawing usually have a frequency characteristics similar to that of a first order low pass filter but the phase characteristics is not that of a first order low pass filter. Instead the phase characteristic is almost linear, i.e. there is a substantially constant group delay.
  • the group delay resulting from applying the correction filter according to Fig. 7 is shown. Assuming the rest of the link to be substantially phase linear/having a constant group delay, the total group delay deviation is caused by the correction filter only. Below 2.5 MHz there is no signal for 100BASE-TX and at 2.5 MHz the period time equals 400 ns where thus the deviation, ⁇ 8 ns is a very small fraction of the period time. Actual information signals span from ⁇ 12 to ⁇ 32 MHz plus harmonics. For every frequency, delay deviation is very much smaller than the respective period. Still the remaining fault would cause some distortion of the signal. By relaxing the demands on perfect frequency characteristics match, a better phase linearity could be obtained possibly resulting in improved bit error ratio. Alternatively, a more elaborate filter would have to be used.
  • the signal arriving from the TP cable enters a simple connector and is fed to the primary winding of an isolation transformer.
  • the secondary winding of the transformer is connected, to ground at one end and at the other end to a voltage divider having a total resistance equal to the matching impedance of the cable (if the ratio of the transformer is 1:1, else appropriate change will be made such that the cable sees a matching impedance) thereby accomplishing a differential to single ended conversion.
  • An appropriate fraction of the signal is fed forward via a capacitor, performing DC blockage, and added to a high impedance DC bias network, the DC voltage modulated by the signal from the capacitor fed to a transimpedance amplifier that converts the voltage to a corresponding electrical current flowing through a LED or a laser diode (LD).
  • a transimpedance amplifier that converts the voltage to a corresponding electrical current flowing through a LED or a laser diode (LD).
  • the light output is not strictly proportional to the current, this resulting in distortion.
  • the modulation is kept at a low fraction of the average current.
  • the light generated by the LED or LD is coupled to the fiber by an optical connector. In the optical to electrical conversion seen in Fig. lib the light output from the fiber is coupled to a photo diode by an optical connector. The photo diode is back biased.
  • the resulting current which is a replica of the light intensity is converted by a transimpedance amplifier to a proportional voltage.
  • the transimpedance amplifier may or may not have internal automatic gain control (AGC) which is governed by the average light level.
  • AGC automatic gain control
  • This solution implies that varying the modulation of the light in the transmitter does not involve this AGC as varying the modulation does not change the average value. Changing the loss of the fiber, however, will change the average value and thus the AGC will be active to compensate for it. If this AGC function would work completely, there would be no need for any further AGC functionality after the transimpedance amplifier.
  • a correction filter may have to be connected between the transimpedance amplifier and the variable gain amplifier, hi principle this correction filter could be connected anywhere in the chain of components but this position is advantageous not loading the filter due to the high input impedance of the variable gain amplifier.
  • the signal passes the peak detector, and enters a transformer for single ended to differential conversion at the same time as impedance matching to the TP cable can be achieved by a proper ratio selection of the transformer, matching the output impedance of the variable gain amplifier to that of the TP cable connected through a TP connector.
  • the correction can be made e.g. by carefully selecting the components in the optical link, utilizing the non-ideal characteristics of such specially selected components.
  • the correction can also be made by e.g. adjusting the frequency responses of the amplifiers included in the optical link portion, see Figs. 11a and 1 Ib. As normally the feedback of a transimpedance amplifier is not accessible this adjustment will only involve the transconductance amplifier of the optical transmitter and the AGC amplifier of the receiver.
  • the digital, part-fiber link as described herein needs significantly less power than the amplifiers and drivers in the conventional FX equipment.
  • the direct conversion as described herein does not use full detection, decoding and re-coding etc., further significantly less power is used as compared to conventional media converters that include TP terminating equipment and protocol conversion.
  • the part-fiber digital link as described herein implies using the ability of the PHY circuits of all TX receivers to compensate for frequency dependent losses of Cat 5 TP cables using dynamic equalizers.
  • the remaining compensation ability of the TX receivers is used to compensate for the non ideal optical link provided that the loss and phase linearity characteristics of the optical link is sufficiently close to that of a Cat 5 TP cable of that equivalent length and that the optical link does not add more than insignificant amounts of noise and other types of distortion not caused by TP cables to the signal.
  • the amplifiers and drivers involved will use much less power compared to a conventional FX link. In the vast majority of all optical fiber link installations this restricted Cat 5 TP cable length is not of any concern.
  • Layer Dependent sublayer technology also called as CDDI (and compared to Ethernet standard 802.3u using the ANSI X3T9.5 FDDI Physical Layer Dependent (fiber PMD) standard for fiber communication).
  • CDDI Layer Dependent sublayer technology
  • fiber PMD Physical Layer Dependent
  • the solution would also work for any other system/communication standard designed for metallic wires including dynamic (or fixed) equalizers compensating for frequency dependent losses of varying (or fixed) lengths of metallic wires.
  • the kind of optical link as described herein would still replace a specific length of metallic wire and the remaining, lengths of metallic wire could still be chosen arbitrarily on either side of the optical link provided that the total length, the sum of the metallic cable parts and the equivalent length (L eq ), is equal to that length for which the fixed equalizers are designed to compensate.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Communication System (AREA)

Abstract

L'invention concerne une liaison optique comprenant une fibre optique (35) pour une transmission de signaux, et ayant d'une borne d'entrée électrique à une borne de sortie électrique une perte liée à la fréquence et des caractéristiques de linéarité de phase égales ou similaires, pour au moins une zone de fréquence particulière ou prédéterminée, à une longueur spécifique d'un câble électrique, tel qu'un câble en paire torsadée, indépendamment de la longueur réelle de la fibre optique, naturellement dans certaines limites plutôt larges. La liaison optique peut comprendre à cette fin des composants sélectionnés spécialement ou des dispositifs de compensation tels que des filtres (41) ou d'autres dispositifs configurés de manière appropriée.
EP08767064.2A 2007-06-11 2008-06-11 Liaison optique Withdrawn EP2156578A4 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE0701485 2007-06-11
PCT/SE2008/000391 WO2008153470A1 (fr) 2007-06-11 2008-06-11 Liaison optique

Publications (2)

Publication Number Publication Date
EP2156578A1 true EP2156578A1 (fr) 2010-02-24
EP2156578A4 EP2156578A4 (fr) 2016-07-13

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EP08767064.2A Withdrawn EP2156578A4 (fr) 2007-06-11 2008-06-11 Liaison optique

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FR3100626B1 (fr) * 2019-09-05 2022-12-23 Terega Systeme de transfert unidirectionnel de donnees et procede correspondant
CN115483982B (zh) * 2022-08-30 2024-06-21 西北核技术研究所 一种模拟光链路输入信号测量方法及装置

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AU6052998A (en) * 1997-02-03 1998-08-25 Reltec Corporation Distributed ethernet hub
SE0003257D0 (sv) * 2000-09-13 2000-09-13 Hesselbom Innovation & Dev Hb Nät innefattande omvandlare mellan elektriska och optiska signaler
JP2003198594A (ja) * 2001-12-25 2003-07-11 Sumitomo Electric Ind Ltd メディアコンバータ
JP2004032411A (ja) * 2002-06-26 2004-01-29 Sumitomo Electric Ind Ltd 光受信器および光通信システム

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EP2156578A4 (fr) 2016-07-13

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