TW201433107A - System and method for multiple sub-octave band transmissions - Google Patents

Abstract

A system and method for enabling multiple sub-octave band transmissions with reduced second order distortions is provided. For this method, first and second sub-octave bands are established. The second sub-octave band is spaced from the first sub-octave band by a non-transmission band. Digital signals are modulated onto RF carrier frequencies in the first and second band to produce first band RF signals and second band RF signals. The first and second band signals are converted into one or more light beams and transmitted over a fiber optic cable. After transmission, an optical receiver reconverts the light beam into an RF signal. Second order distortions outside a selected sub-octave band can be filtered from RF signal and a tuner used to tune in a selected carrier frequency. A receive modem can then be used to demodulate the tuned carrier frequency for receipt of its respective digital signal.

Description

System and method for multiple sub-octave transmissions

This application is a continuation-in-part application of the inventor of December 28, 2010, to the Japanese Patent No. 12/980,008 (Attorney Docket No. 11576.2), the entire contents of which are hereby incorporated by reference. The manner is incorporated herein.

The present invention is generally directed to systems and methods for enabling data transmission via optical fibers. More particularly, the present invention relates to systems and methods for transmitting digital signals over a fiber optic network and then performing subsequent sub-multiplication filtering to remove second order distortion from the signals. The invention is particularly, but not exclusively, useful as a system and method for transmitting digital signals using a passive optical network (PON) and then performing sub-multiplication filtering.

A passive optical network (PON) is essentially an optical network that uses a single fiber optic cable to transmit signals from one point (eg, a service provider) to a plurality of different points (eg, a client). The signal to be transmitted is likely to be a digital signal. Thus, in addition to the fiber optic cable, the PON will necessarily include components (i.e., data machines) that modulate the digital signal to the radio frequency (RF) carrier at the transmission end of the fiber optic cable. The resulting RF signal is then converted to an optical signal for transmission via a fiber optic cable. At the receiving end of the fiber optic cable, the program is reversed. In particular, the component (data machine) reconverts the optical signal to an RF signal and then demodulates the RF signal for subsequent use.

An important aspect of PON is that it can utilize well-known optical signal transmission by split-wave multiplexing (WDM). This splitting multiplex essentially allows the PON to use one wavelength (λ ₁ ) for downstream traffic (λ ₂ ) on the fiber optic cable while simultaneously using another wavelength (λ ₂ ) for upstream traffic. In addition, it is possible to have two or more upstream traffic wavelengths (eg, λ ₁ and λ ₃ ) and two or more downstream traffic wavelengths (eg, λ ₂ and λ ₄ ). This WDM capability coupled to the point-to-multipoint nature of the PON gives the PON a unique advantage over other types of network architectures. In particular, the PON configuration will reduce the amount of fiber optic cable required relative to the point-to-point architecture. However, a potential drawback is that known fiber optic cables introduce distortion into the optical signal that will attenuate the clarity of the optical signal.

Of all the distortions that can be introduced into the optical signal as the optical signal is transferred via the fiber optic cable, the most dominant distortion is second order distortion. However, such second order distortions are relatively easily identified. For example, consider the RF frequencies f _a and f _b carrying optical signals. As the optical signal is transferred via the fiber optic cable, it may happen that the fiber optic cable induces two RF distortion signals at frequencies f _a +f _b and f _a -f _b into the optical signal. In f _a In the case of f _b , the second-order distortion is f _a +f _b 2f _a and f _a -f _b 0. In this case, f _a -f _b 0 is unimportant, and 2f _a defines the frequency multiplication of f _a .

In view of the above, it is an object of the present invention to provide a passive optical network having a submultiplier filter such that a clear signal will be transmitted via the PON with minimal (if any) distortion at the receiving end of the transmission. Another object of the present invention is to provide a passive optical network that effectively removes distortion from the fiber optic cable of the PON to the signal from the transmitted signal. It is yet another object of the present invention to provide a system and method for transmitting a digital signal over an RF carrier frequency within a plurality of sub-octave bands such that second order distortion is reduced. Another object of the present invention is to use RF carrier frequencies within multiple sub-octave bands to increase transmission bandwidth and reduce second order distortion. It is yet another object of the present invention to provide a system and method for multiple sub-octave transmissions that are easy to use, simple to use, and relatively cost effective.

According to the invention, a passive optical network (PON) has a bandpass filter, the bandpass A filter is used to remove second order distortion induced by a beam of light transmitted through a fiber optic cable in the PON from an optical signal. In accordance with the present invention, the optical signal from the fiber optic cable is converted to an RF signal and the RF signal is filtered in a sub-multiple bandwidth of the RF carrier frequency including the digital signal. The RF signal can then be demodulated for subsequent reception of the digital signal.

Structurally, the passive optical network (PON) of the present invention includes a transmission data machine for modulating a plurality of digital signals to respective RF carrier frequencies (f). This operation can be performed by amplitude modulation, frequency modulation, or phase modulation. An optical transmitter having the data machine is also used to convert each of the modulated carrier frequencies into an optical signal. The optical signal is then combined with other similarly formed optical signals using a split multiplexer (WDM) to produce a beam of light. Importantly, in this beam, each optical signal will have its own individual wavelength (λ).

For the present invention, a fiber optic cable is provided for transmitting the light beam between an optical line terminal (OLT) [e.g., a service provider] and a plurality of optical network units (ONUs) [e.g., a user terminal] via the PON. . In detail, the fiber will have a first end connected to the OLT for receiving the beam from the transmitter and the WDM. The beam is then transmitted via the fiber to the second end of the fiber. A beam splitter connected to the second end of the fiber is used to divide the beam into a subset. As contemplated by the present invention, each subset is transmitted to a respective ONU, and each subset will include all of the optical signals in the transmitted beam, but with reduced power.

A plurality of optical receivers are positioned at respective subscriber ends (i.e., ONUs) in the network to receive a subset from the beam. Each optical receiver then acts in conjunction with the data machine to reconvert the optical signals in the subset back to their respective modulated carrier frequencies. The sub-octave band pass filter then filters out second order distortion outside the submultiple of the modulated carrier frequency. Therefore, the second order distortion is removed from the received signal.

Once the received signal has been reconverted and filtered, the tuner is used Tuning in the selected carrier frequency and directing the selected carrier frequency to the addressed end of the OUN. The receiving data machine then demodulates the tuned carrier frequency to reconstruct its respective digital signal. The digital signal can then be used for its intended purpose.

Operationally, the method of the present invention for implementing sub-multiplication transmission of a digital signal via a passive optical network (PON) relies on establishing a sub-multiple bandwidth for each of a plurality of discrete carrier frequencies (f). Initially, the method contemplates modulating the digital signal to a selected carrier frequency (f) and then converting the modulated carrier frequency to an optical signal. By this conversion, both the optical signal and the digital signal will have the same wavelength (λ). A plurality of such optical signals can be correspondingly formed and combined together into the light beams. In this case, a beam of light is introduced into the first end of the fiber optic cable and the beam is transmitted from the first end to the second end via the fiber optic cable.

At the second end of the fiber optic cable, the beam is divided into a number of subsets, each of which includes all of the optical signals of the originally transmitted beam. Each subset of the beams is then directed to a designated optical receiver at each ONU where each subset is reconverted to a modulated carrier frequency. In this regard, the modulated carrier frequency filters out second order distortion outside of the established submultiplier. A tuner can then be used to tune in the selected modulated carrier frequency, and a receive modem can be used to demodulate the variable tuned carrier frequency for receiving its respective digital signal.

As contemplated by the present invention, establishing a submultiplier involves identifying a first multiplier that is delimited by a low carrier frequency (f _L1 ) and a high carrier frequency (f _H1 ). This first multiplier will be used by the forward (downstream) transmission beam. Importantly, 2f _L1 f _H1 >f _L1 . Also, a second frequency multiplied by a low carrier frequency (f _L2 ) and a high carrier frequency (f _H2 ) is identified. This second multiplier will be used by the return (upstream) receive beam, where 2f _L2 f _H2 >f _L2 . For the present invention, the forward (downstream) transmitted beam and the return (upstream) received beam will include a carrier frequency in the range between 750 MHz and 40 GHz. Additionally, embodiments of the present invention are contemplated to use two PONs on the same fiber optic cable. For such embodiments, the present invention contemplates adding a bandwidth below f _L1 for the forward (downstream) transmission beam (eg, λ ₃ ) to be used in the second PON, and adding a bandwidth below f _L2 for The return (upstream) receive beam (eg, λ ₄ ) is used in the second PON.

In another aspect of the invention, a system and method for implementing multiple sub-octave transmissions with reduced second order distortion is provided. For this aspect of the invention, a first sub-octave band having a plurality of discrete carrier frequencies extending from F ₁ to F ₂ is established, where F ₂ < 2F ₁ . Where the first sub-octave band has been established, the digital signal is modulated to the RF carrier frequency in the first frequency band to produce a first frequency band RF signal. Furthermore, for this aspect, extends to create custom F ₃ having a second plurality of discrete sub-octave band carrier frequency F _4, wherein _{F 4 <F 1 + F 3} . Where the second sub-octave band has been established, the digital signal is modulated to the RF carrier frequency in the second frequency band to produce a second frequency band RF signal.

For this aspect of the invention, the second sub-octave band is separated from the first sub-multiple band by a non-transmission band (i.e., a non-transmission band between F ₂ and F ₃ ). Furthermore, to reduce second-order distortion, a non-transmission band is established, where F ₃ >2F ₂ . Additional frequency bands above or below the first frequency band may be used. The bandwidth of the non-transmission band between the additional frequency bands and the frequency bands can be calculated using the techniques provided herein to reduce or eliminate the effects of second order distortion. Typically, the frequency in the frequency band described above is in the range of frequencies between 750 MHz and 40 GHz.

Typically, an up-converter is used to modulate the digital signal into the sub-octave band. For example, the machine may first data modulated digital signal to the original RF carrier frequency F ₀ so as to generate the modulated RF signal of the original. Next, the initially modulated RF signal is upconverted from carrier frequency F ₀ to a carrier frequency within the first frequency band (ie, upconverted to a frequency between F ₁ and F ₂ ). It will be appreciated that up-conversion can be used to modulate the digital signal into other sub-octave bands (i.e., the second and third bands described above).

In the case where the digital signal has been modulated on the carrier frequency within the first frequency band and the second frequency band (or third frequency band, if applicable), the first frequency band signal and the second frequency band signal are converted into one or more light beams. For example, one or more transmitters can be used to convert the first frequency band signal and the second frequency band signal into one or more light beams. In one embodiment, the first band RF signal and the second band RF signal are first combined into a combined RF signal, and the combined RF signal is converted to a beam by a transmitter. In some cases, the first frequency band signal and the second frequency band signal into a light beam having a wavelength (λ ₁₎ of, and prior to transmission, using WDM having a wavelength (λ ₁₎ of this light beam with a wavelength ([lambda] having ₂ ) The other beam is multiplexed together. For example, a beam of wavelength (λ ₂ ) can be produced by another system of similar configuration.

Next, a beam of light is introduced into the fiber optic cable for transmission via the fiber optic cable. For example, a light beam having a first frequency band signal and a second frequency band signal can be introduced into the same end (ie, the first end) of the fiber optic cable for transmission to the second cable end. In some cases, the first frequency band signal and the second frequency band signal are converted into a light beam having a wavelength (λ ₁ ), and the wavelength multiplexing (λ ₁ ) is used before the light beam is introduced into the optical fiber cable. The beam is multiplexed with another beam having a wavelength (λ ₂ ). At the second end of the fiber optic cable, the digital signal can be recovered from the beam. For example, the first frequency band signal can be drawn from the beam at the second end by first dividing the beam received at the second end of the fiber optic cable into a subset of all of the signals including the originally transmitted beam. Each subset of the beams is then directed to a designated optical receiver, and each subset is reconverted to an RF signal at a designated optical receiver. In this regard, second order distortion outside the first sub-octave band is filtered from the RF signal, for example, using a bandpass filter. A tuner can be used to tune in the selected modulated carrier frequency in the first frequency band. A receive modem can be used to demodulate the tuned carrier frequency from the tuner for receiving its respective digital signal. A similar procedure can be used to recover digital signals in other sub-octave bands, such as the second sub-multiple band.

10‧‧‧ Passive Optical Network (PON)

12‧‧‧Fiber Cable (Fiber Optic)

14‧‧‧ Optical Line Terminal (OLT)

16‧‧‧Optical Network Unit (ONU)

18‧‧‧ digital signal

20‧‧‧Data machine

22‧‧‧Modulated carrier frequency (f ₁ )

22'‧‧‧Modulated carrier frequency (f ₁ )

24‧‧‧Transmitter

26‧‧‧ Optical signals

28‧‧‧Dividing multiplexer (WDM)

30‧‧‧ Beam

30'‧‧‧Subset beam

32‧‧‧Distributor

34‧‧‧Dividing multiplexer (WDM)

36‧‧‧Optical Receiver

38‧‧‧Bandpass filter

40‧‧‧Receiving data machine

42‧‧‧ digital signal

44‧‧‧Modulated carrier frequency (f ₂ )

44'‧‧‧Modulated carrier frequency (f ₂ )

46‧‧‧Transporter

48‧‧‧ optical signal

50‧‧‧ Beam

52‧‧‧ Receiver

54‧‧‧Bandpass filter

56‧‧‧Stepwise method

58‧‧‧ Block

60‧‧‧ blocks

62‧‧‧ Block

64‧‧‧ Block

66‧‧‧ Block

68‧‧‧ Block

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78‧‧‧ Block

80a‧‧‧Sub-multiplier carrier band/first band

80b‧‧‧Second submultiplier carrier band

80c‧‧‧ third submultiplier carrier band

82a‧‧‧Non-transmission band

82b‧‧‧Non-transmission band

The novel features of the present invention, as well as the description of the present invention, as well as the <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; 1 is a schematic layout of constituent elements of a passive optical network (PON) according to the present invention; 2 is a flow chart showing the operation of the method of the present invention; and FIG. 3 is a frequency diagram showing a sub-multiplied carrier frequency band separated by a non-transmission band.

Referring initially to Figure 1, a component of a passive optical network (PON) in accordance with the present invention is shown, generally designated generally 10 as a passive optical network (PON). As shown, the PON 10 includes a fiber optic cable (fiber) 12 that interconnects an optical line termination (OLT) 14 (eg, a service provider) with a plurality of optical network units (ONUs) 16 (eg, subscribers) . In FIG. 1, ONU 16 is merely illustrative and is shown as serving client A.

As indicated in FIG. 1, the digital signal 18 to be transmitted via the PON 10 is modulated by the data machine 20. For PON 10 purposes, this modulation can be amplitude modulation, frequency modulation, phase modulation, or any combination of the three. In any event, the digital signal 18 is modulated to the RF carrier frequency (f ₁ ) in a manner well known in the related art. In Figure 1, showing the establishment of a sub-carrier frequency f low and high _Ll carrier frequency f _H1 delimiting the second harmonic of the modulated carrier frequency 22 (i.e., f _1). Once the submultiplier is established, the now modulated carrier frequency 22 is passed to the transmitter 24 where the carrier frequency 22 is converted to an optical signal 26 (i.e., an optical signal having a wavelength λ ₁ ). . Again, the optical signal 26 (λ ₁ ) is sent to a split multiplexer 28 (WDM) where it is combined with other optical signals (eg, λ ₃ ) into a beam 30 for passage via The fiber optic cable 12 is transported downstream. As shown in FIG. 1, fiber optic cable 12 is coupled between WDM 28 and beam splitter 32.

After the optical signal 26 on the beam 30 has been transmitted by the fiber optic cable 12, the beam 30 is split into a plurality of subset beams 30' at the beam splitter 32. Importantly, each subset of beams 30' includes all optical signals (eg, λ ₁ and λ ₂ ) that are combined together at WDM 28. In addition, each subset of beams 30' is then sent to a respective ONU 16. In operation, WDM 34 at ONU 16 (i.e., client A) receives the same subset of beams 30' as the subset of beams received by each of the other ONUs 16 (e.g., client X). For a particular instance of client A, the optical signal (λ ₁ ) 26 in the subset of beams 30' received by the ONU 16 is sent to a receiver 36 where it is reconverted to its modulated carrier. Frequency 22' (ie, f ₁ ). This modulated carrier frequency 22'(f ₁ ) is then filtered by bandpass filter 38 and demodulated by modem 40. The result of this operation is the receipt of a digital signal 18 carried by the filtered carrier frequency 22' at the ONU 16, wherein all damage caused by second order distortion is effectively removed from the digital signal 18.

Although the above disclosure focuses on downstream transmissions from the OLT 14 to the ONU 16, the upstream transmissions from the ONU 16 to the OLT 14 operate similarly and essentially inversely. In particular, for upstream transmission, the digital signal 42 is modulated at the data machine 40 to an RF carrier frequency (f ₂ ) in a similar manner as disclosed above for f ₁ . In this example, the modulated carrier frequency 44 (i.e., f ₂ ) is established in a _submultiple that is delimited by the low carrier frequency f _L2 and the high carrier frequency f _H2 . The modulated carrier frequency 44 is then passed to a transmitter 46 where it is converted to an optical signal 48 (i.e., an optical signal having a wavelength λ ₂ ). Again, the optical signal 48 (λ ₂ ) is sent to a split multiplexer 34 (WDM) where it can be combined with other optical signals (eg, λ ₄ ) into a beam 50 for passage via The fiber optic cable 12 is transported upstream. The beam 50 is then received by the OLT 14, processed via the split multiplexer 28 and sent to the receiver 52 where the optical signal 48 in the beam 50 is reconverted to its modulated carrier frequency 44' (also That is, f ₂ ). This modulated carrier frequency 44 (f ₂ ) is then filtered by a bandpass filter 54 which is then demodulated by the modem 20. The result of this operation is the reception of a digital signal 42 at the OLT 14, wherein the self-digital signal 42 effectively removes all damage caused by second order distortion.

2 presents a step-by-step method (generally designated 56) indicating that the initial consideration for the operation of PON 10 is to establish a submultiplier (see block 58). Specifically, a submultiple is established for each transmission (downstream/upstream). To transmit digital signal 18/42 via PON 10, block 60 indicates that digital signal 18/42 is modulated to carrier frequency 22(f ₁ )/44(f ₂ ). Block 62 then instructs to convert the modulated carrier frequency 22(f ₁ )/44(f ₂ ) into an optical signal 26(λ ₁ )/48(λ ₂ ). The optical signal 26(λ ₁ )/48(λ ₂ ) can then be combined with other such signals at WDM 28/34 and transmitted as a beam 30/50 via fiber optic cable 12 (downstream/upstream) (see block 64) .

In the context of specifically relating to the beam 30, block 66 indicates that the beam 30 is divided into a plurality of subset beams 30'. Each subset beam 30' is then directed to a particular ONU 16 (see block 68) where the subset beam is converted back from the optical signal 26(λ ₁ )/48(λ ₂ ) (see Block 70) to RF modulated carrier frequency 22(f ₁ )/44(f ₂ ). The RF modulated carrier frequency 22(f ₁ )/44(f ₂ ) is then filtered (see block 72). More specifically, as indicated above, a unique submultiplier is established for each of the band pass filters 38 and 54 to be used from the downstream beam 30 and after the beam 30/50 has been transmitted by the fiber optic cable 12, respectively. The second order distortion is removed from the upstream beam 50.

The optical signal 26(λ ₁ )/48(λ ₂ ) has been reconverted into individual RF modulated carrier frequencies 22'(f ₁ )/44'(f ₂ ) and has been modulated by RF After carrier frequency 22'(f ₁ )/44'(f ₂ ) removes second-order distortion, block 74 indicates that the user can tune for the carrier frequency of interest (eg, modulated carrier frequency 22(f ₁ )) . The modulated carrier frequency 22(f ₁ ) is then demodulated by the data machine 20/40 (see block 76) and the digital signal 18/42 is received for use, wherein no second order distortion is caused in the transmission procedure. Any significant damage (see block 78).

3 is a frequency diagram showing sub-multiplied carrier frequency bands 80a through 80c that may be used to transmit signals via a common optical transmission path and reduce second order distortion. As shown, established to extend from F ₁ and F ₂ having a frequency bandwidth such that a first sub-band 80a F ₂ <2F _1's. For the first frequency band 80a, a plurality of discrete RF carrier frequencies (such as F _a and F _b ) can be modulated by, for example, the data unit 20 shown in FIG. 1 by respective digit signals to produce a respective first Band RF signal. As shown, established extending from F ₃ to F ₄ and having a frequency bandwidth such that the second sub-band _{80b F 4 <F 1 + F} 3 of. For the second sub-multiplied carrier frequency band 80b, a plurality of discrete RF carrier frequencies (such as F _c and F _d ) can be modulated, for example, by using the data unit 20 shown in FIG. 1 by respective digit signals to generate Individual second band RF signals. Figure 3 shows a further third sub may establish extends from F ₅ to F ₆ (where _{F 6> F 5> F 4} ) of carrier frequency bands 80c. For the third frequency band 80c, a plurality of discrete RF carrier frequencies (such as F _e and F _f ) can be modulated, for example, by the data unit 20 shown in FIG. 1 by respective digit signals to produce a respective third Band RF signal. Although three sub-multiplied carrier bands 80a through 80c are shown in FIG. 3 and described herein, it should be appreciated that more than three and only two sub-multiplied carrier bands 80a through 80c can be used as part of a multi-subband octave transmission system.

Figure 3 further shows that the sub-multiplied carrier bands 80a through 80c are separated by non-transmission bands 82a, 82b. Specifically, as shown, the sub-multiplied carrier frequency band 80a is separated from the sub-multiplied carrier frequency band 80b by the non-transmission frequency band 82a, and the sub-multiplied carrier frequency band 80b is sub-multiplied by the non-transmission frequency band 82b. The carrier frequency band 80c is separated.

The non-transmission bands 82a, 82b are sized to have sufficient bandwidth to reduce second order distortion. For example, a non-transmission band 82a having a bandwidth such that F ₃ > 2F ₂ is established (i.e., the non-transmission band 82a has a bandwidth greater than a multiplier). In this configuration, the second-order distortion (including 2F ₁ , 2F ₂ , F ₁ +F _{2 ,} and F ₂ -F ₁ ) from the sub-multiplied carrier band 80a will not interfere with the sub-multiplied carrier band 80b and is derived from the sub-times order distortion frequency carrier band 80b (including _{2F 3, 2F 4, F 3} + F 4 and F ₄ -F ₃₎ will not interfere with the sub-carrier frequency band 80a.

When the actual frequencies F ₁ , F ₂ , F _{3 ,} and F ₄ have been determined, the bandwidth of the third frequency band (that is, the sub-multiplied carrier frequency band 80c) and the non-transmission frequency band 82b can be determined. In particular, the non-transmission band between 2F ₃ and 2F ₄ will ensure that second order distortion between sub-multiplier carrier band 80b and sub-multiplier carrier band 80c is reduced or eliminated. Specifically, in this configuration, the second-order distortion (including 2F ₃ , 2F ₄ , F ₃ + F _{4 ,} and F ₄ -F ₃ ) from the sub-multiplied carrier band 80b will not interfere with the sub-multiplied carrier band 80c, And the second order distortion (including 2F ₅ , 2F ₆ , F ₅ + F _{6 ,} and F ₆ -F ₅ ) from the sub-multiplied carrier band 80c will not interfere with the sub-multiplied carrier band 80b.

A third frequency band (i.e., sub-multiplied carrier frequency band 80c) can be established, where F ₅ > 2F ₄ and F ₆ < F ₅ + F ₁ . In some cases, depending on frequency sub-carriers 80a and 80b and a non-transmission band size band 82a, the third frequency band (i.e., sub-carrier frequency band 80c) may comprise less than the carrier frequency 2F _3. For this condition, you can create sub-carrier frequency band 80c, where F _5> F ₂ + F ₄ and less than 2F ₃ F ₆ or F ₁ + F ₅ in the smaller. Typically, the frequency in the sub-multiplied carrier frequency bands 80a through 80c is in the range of frequencies between about 750 MHz and about 40 GHz.

Continuing with Figure 3, an upconverter (not shown) can be used as part of the data engine 20 (shown in Figure 1) to modulate the digital signal into the sub-multiplied carrier bands 80a through 80c. For example, machine 20 may first use the number of data bits to the original RF signal modulated on the carrier frequency F ₀ (see FIG. 3), to generate an RF modulated signal via the original. Next, the initially modulated RF signal is upconverted from carrier frequency F ₀ to a carrier frequency within one of the submultiplied carrier bands 80a through 80c.

In the case where the digital signal has been modulated on the carrier frequency within the sub-multiplied carrier frequency bands 80a through 80c, the signal can be converted to a light beam having a wavelength (λ ₁ ) using the transmitter 24 as shown in FIG. As also shown in FIG. 1, a beam having a wavelength (λ ₁ ) can be multiplexed with other beams, such as a beam having a wavelength (λ ₂ ), using split multiplex 28 .

Continuing with Figure 1, a beam of light can then be introduced into the fiber optic cable 12 for transmission. At the second end of the fiber optic cable 12, the digital signal can be recovered from the beam. For example, the beam received at the second end of the fiber optic cable 12 can be first split at the second end at the second end by splitting the beam received at the second end of the fiber optic cable 12 at the splitter 32 into a subset of all of the signals including the originally transmitted beam. A signal from the sub-multiplied carrier frequency band 80a. Each subset of the beams is then directed to a designated optical receiver 36 where it is reconverted to an RF signal. In this regard, second order distortion outside the sub-multiplied carrier frequency band 80a is filtered from the RF signal, for example, using a bandpass filter 38. A tuner can be used to tune in the selected modulated carrier frequency in the sub-multiplied carrier frequency band 80a. Receiver data machine 40 can be used to demodulate the tuned carrier frequency for receiving its respective digital signal. A similar procedure can be used to recover the digital signals in the other sub-multiplied carrier frequency bands 80a through 80c, such as the sub-multiplied carrier frequency band 80b and the sub-multiplied carrier frequency band 80c.

Although the particular passive optical network with sub-multiplied transmission as shown and disclosed in detail herein is fully capable of achieving the objectives previously set forth herein and providing the prior art herein. The advantages of the description are to be understood as being merely illustrative of the presently preferred embodiments of the invention, and are not intended to limit the details of the construction or design shown herein.

56‧‧‧Stepwise method

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60‧‧‧ blocks

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76‧‧‧ Block

78‧‧‧ Block

Claims (20)

A method for implementing multiple sub-octave transmissions with reduced second-order distortion, the method comprising the steps of: establishing a first sub-octave band having one of a plurality of discrete carrier frequencies, including F ₁ and F ₂ , wherein F ₂ >F ₁ ; modulating the digital signal to a radio frequency (RF) carrier frequency in the first frequency band to generate a first frequency band RF signal; establishing a second sub-multiple frequency band having a plurality of discrete carrier frequencies, including F ₃ And F ₄ , wherein F ₄ > F ₃ , and wherein the second frequency band is separated from the first frequency band by a non-transmission band between F ₂ and F ₃ , wherein F ₃ &_gt; 2F ₂ ; Transmitting a signal to an RF carrier frequency in the second frequency band to generate a second frequency band RF signal; converting the first frequency band signal and the second frequency band signals into one or more light beams; and the one or more The light beam is introduced into a fiber optic cable for transmission via the fiber optic cable. The method of claim 1, wherein the first frequency band extends from F ₁ to F ₂ and the second frequency band extends from F ₃ to F ₄ . The method of claim 1, wherein F ₂ < 2F ₁ . The method of claim 1, wherein F ₄ <F ₁ +F ₃ . The method of claim 1, wherein the first frequency band signals and the second frequency band signals are introduced into the same end of the fiber optic cable in the introducing step. The method of claim 1, wherein the step of modulating the digital signal to a radio frequency (RF) carrier frequency in the first frequency band to generate the first frequency band RF signal comprises the substep of: translating a digital signal to a An initial RF carrier frequency F ₀ to generate an initially modulated RF signal; and upconverting the initially modulated RF signal to upconvert the carrier frequency F ₀ to a carrier in the first frequency band frequency. The method of claim 1, wherein the converting step converts the first frequency band signal and the second frequency band signals into a light beam having a wavelength (λ ₁ ). The method of the requested item 7, further comprising the step of: prior to the introducing step, the use of WDM light beam having the wavelength (λ ₁₎ and the other beam having the wavelength multiplexing together (λ ₂₎ of the. The method of claim 1, further comprising the step of combining the first frequency band signals and the second frequency band signals into a combined RF signal prior to the converting step. The method of claim 1, further comprising the steps of: establishing a third sub-octave band having one of a plurality of discrete carrier frequencies, including F ₅ and F ₆ , wherein F ₆ > F ₅ , and wherein the third band is Separating from the second frequency band by a non-transmission band between F ₄ and F ₅ , where F ₅ >2F ₄ ; modulating the digital signal to the RF carrier frequency in the third frequency band to generate a third a frequency band RF signal; and wherein the converting step converts the first frequency band signal, the second frequency band signals, and the third frequency band signals into one or more light beams; and wherein the introducing step will have the first frequency band signals The one or more beams of the second frequency band signals and the third frequency band signals are introduced into a fiber optic cable for transmission via the fiber optic cable. The method of claim 1, further comprising the steps of: recovering a first frequency band signal from a beam of the fiber optic cable; filtering the recovered first frequency band signal from the first sub-octave band Second order Distortion; and demodulating from the filtered first frequency band signal to a digital signal. The method of claim 11, wherein the filtering step is performed using a band pass filter. The method of claim 1, wherein the frequency F ₁ is in a range of frequencies between 750 MHz and 40 GHz. A method for multiple sub-octave transmissions of a signal, the method comprising the steps of: modulating a digital signal to an RF carrier frequency in a discrete first sub-multiple frequency band and a second sub-multiple frequency band to generate a first first a frequency band signal and a second frequency band signal, wherein the first frequency band is separated from the second frequency band by one or more frequency multiplications; and converting the first frequency band signal and the second frequency band signals into one or more light beams for Transmitting via a fiber optic cable; recovering a first frequency band signal from a beam of the fiber optic cable; filtering the second frequency distortion outside the first submultiple band from the recovered first frequency band signal; and The filtered first frequency band signal is demodulated into a digital signal. The method of claim 14, wherein the first frequency band extends from F ₁ to F ₂ , the second frequency band extends from F ₃ to F ₄ , and the second frequency band is by a non-F ₂ and F ₃ The transmission band is spaced apart from the first band, where F ₃ > 2F ₂ . The method of claim 15, wherein F ₂ < 2F ₁ and F ₄ < F ₁ + F ₃ . A system for multiple sub-octave transmissions of signals, comprising: at least one data machine modulating a digital signal to an RF carrier frequency in a first sub-multiple frequency band and a second sub-multiple frequency band to generate a first frequency band a signal and a second frequency band signal; at least one transmitter, the first frequency band signals and the second frequency band signals Converting into one or more light beams for transmission via a fiber optic cable; a receiver that recovers a first frequency band signal from a beam of the fiber optic cable; a band pass filter from which the recovered A frequency band signal filters out second order distortion outside the first sub-octave band; and a data machine that demodulates the digital signal from the filtered first frequency band signal. The system of claim 17, wherein the first frequency band extends from F ₁ to F ₂ , the second frequency band extends from F ₃ to F ₄ , and the second frequency band is by a non-F ₂ and F ₃ The transmission band is spaced apart from the first band, where F ₃ > 2F ₂ . The system of claim 17, wherein the first frequency band extends from F ₁ to F ₂ , the second frequency band extending from F ₃ to F ₄ , F ₂ < 2F ₁ . The system of claim 19, wherein F ₄ <F ₁ +F ₃ .