IPC분류정보
| 국가/구분 |
United States(US) Patent
등록
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| 국제특허분류(IPC7판) |
|
| 출원번호 |
US-0151996
(1998-09-11)
|
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발명자
/ 주소 |
- Boesch, Ronald D.
- Arpaia, Domenico
|
| 출원인 / 주소 |
|
| 대리인 / 주소 |
Myers Bigel Sibley & Sajovec
|
| 인용정보 |
피인용 횟수 :
81 인용 특허 :
22 |
초록
▼
A narrow bandwidth signal, such as a narrowband FM signal, is modulated in a modulator that modulates a wide bandwidth signal, such as a CDMA signal, by oversampling the narrow bandwidth signal and applying the oversampled narrow bandwidth signal to the modulator. By oversampling the narrow bandwidt
A narrow bandwidth signal, such as a narrowband FM signal, is modulated in a modulator that modulates a wide bandwidth signal, such as a CDMA signal, by oversampling the narrow bandwidth signal and applying the oversampled narrow bandwidth signal to the modulator. By oversampling the narrow bandwidth signal, the same fixed low pass filter can be used for both the wide bandwidth signal and the oversampled narrow bandwidth signal. Accordingly, different low pass filters or switched low pass filters are not needed. The DC offset that is introduced by the digital-to-analog converter and/or the low pass filter of the modulator is compensated, preferably in the digital domain, to thereby reduce DC offset within acceptable limits for the modulation that is being used. More preferably, compensation is provided by subtracting from the sampled signal, a digital value representing the DC offset in the filtered analog signal that is introduced by the digital-to-analog converter and/or the low pass filter. A sensor senses the DC offset in the filtered analog signal. An analog-to-digital converter is responsive to the sensor to convert the sensed DC offset into a digital offset signal. A subtractor is responsive to the analog-to-digital converter to subtract the digital DC offset signal from the sampled signal and to apply the sampled signal minus the DC offset signal, to the digital-to-analog converter.
대표청구항
▼
A narrow bandwidth signal, such as a narrowband FM signal, is modulated in a modulator that modulates a wide bandwidth signal, such as a CDMA signal, by oversampling the narrow bandwidth signal and applying the oversampled narrow bandwidth signal to the modulator. By oversampling the narrow bandwidt
A narrow bandwidth signal, such as a narrowband FM signal, is modulated in a modulator that modulates a wide bandwidth signal, such as a CDMA signal, by oversampling the narrow bandwidth signal and applying the oversampled narrow bandwidth signal to the modulator. By oversampling the narrow bandwidth signal, the same fixed low pass filter can be used for both the wide bandwidth signal and the oversampled narrow bandwidth signal. Accordingly, different low pass filters or switched low pass filters are not needed. The DC offset that is introduced by the digital-to-analog converter and/or the low pass filter of the modulator is compensated, preferably in the digital domain, to thereby reduce DC offset within acceptable limits for the modulation that is being used. More preferably, compensation is provided by subtracting from the sampled signal, a digital value representing the DC offset in the filtered analog signal that is introduced by the digital-to-analog converter and/or the low pass filter. A sensor senses the DC offset in the filtered analog signal. An analog-to-digital converter is responsive to the sensor to convert the sensed DC offset into a digital offset signal. A subtractor is responsive to the analog-to-digital converter to subtract the digital DC offset signal from the sampled signal and to apply the sampled signal minus the DC offset signal, to the digital-to-analog converter. two non-linear interferometers. 5. The light source of claim 1, wherein the two non-linear interferometers comprise: a first of the non-linear interferometers optically coupled to a first side of the polarization beam splitter furthest from the semiconductor optical gain element, the first non-linear interferometer being perpendicular to the main axis; and a second of the non-linear interferometers optically coupled to a second side of the polarization beam splitter, the second non-linear interferometer being parallel to the main axis. 6. The light source of claim 1, wherein each of the non-linear interferometers comprises: a first glass plate optically coupled to a second glass plate, forming a space therebetween; means for introducing a polarization rotation in at least one channel of an optical signal; and means for broadening a bandwidth of a rotated band of the optical signal. 7. The light source of claim 6, wherein the broadening means comprises: (a) a first reflective coating residing inside the space and on the second glass plate; (b) a second reflective coating residing inside the space and on the first glass plate; (c) a phase bias element residing outside the space. 8. The light source of claim 7, wherein the first reflective coating (a) comprises a reflective coating with a reflectivity of approximately 100%. 9. The light source of claim 7, wherein the second reflective coating (b) comprises a reflective coating with a reflectivity of approximately 18%. 10. The light source of claim 7, wherein the phase bias element (c) is a λ/8 waveplate. 11. The light source of claim 6, wherein the introducing means comprises a phase bias element residing inside the space. 12. The light source of claim 11, wherein the phase bias element is a 8/4 waveplate. 13. The light source of claim 6, wherein the introducing means comprises: a reflective coating residing inside the space and on the first glass plate; a first waveplate with a first optical retardance residing inside the space; and a second waveplate with a second optical retardance, optically coupled to the first glass plate and residing outside the space, wherein a combination of values for the first reflectivity, the first optical retardance, and the second optical retardance effects a separation of channels in at least one optical signal into at least two sets, wherein the at least two sets have asymmetrically interleaved pass bands. 14. A light source for an optical network, comprising: an output optical fiber; a semiconductor optical gain element optically coupled to the output optical fiber, creating a main axis, the semiconductor optical gain element comprising a front facet and a rear facet; a polarization beam splitter optically coupled to the rear facet of the semiconductor optical gain element and intersecting the main axis; and two non-linear interferometers optically coupled to the polarization beam splitter, a first of the non-linear interferometers optically coupled to a first side of the polarization beam splitter furthest from semiconductor optical gain element, the first non-linear interferometer being perpendicular to and intersecting the main axis, and a second of the non-linear interferometers optically coupled to a second side of the polarization beam splitter perpendicular to the first face, the second non-linear interferometer being parallel to the main axis. 15. The light source of claim 14, wherein the front facet comprises a high-reflectivity coating or no coating. 16. The light source of claim 14, wherein the rear facet comprises an anti-reflectivity coating. 17. The light source of claim 14, further comprising: a first aspheric lens optically coupled to the rear facet and the polarization beam splitter; a second aspheric lens optica
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