Koji Kikushima

Erbium-doped fiber amplifier for video distribution networks

The possibility of an application of Er-doped fiber amplifiers to AM-FDM (frequency division multiplexing) or FM-FDM video distribution networks is discussed. The measured noise and modulation distortion properties of ER-doped fiber amplifiers are good enough to meet even the severe quality standards set for trunk lines. A carrier-to-noise ratio (CNR) of 57 dB for an AM-FDM transmission was measured. A second-order harmonic distortion (HD2) of less than -56 dB was measured by the monotone method (modulation depth m=50%), and a cross modulation distortion (XM) of less than -63 dB was measured by the two-tone method (m=25%*channel). On the basis of these values, composite second-order distortion (CSO) and XM in a 40-channel transmission were estimated as less than -57 dB and -73 dB, respectively. Significant reduction of noise and modulation distortion is made possible by optimizing the length of Er-doped fiber amplifiers and using input- and output-port isolators. >

A Super Wideband Optical FM Modulation Scheme for Video Transmission Systems

A novel super wideband optical FM modulation scheme that employs an optical heterodyne detection technique is proposed and demonstrated. The experimental results show that applying this scheme to 40-channel AM video transmission expands the power budget by approximately 10 dB at a carrier- to-noise ratio (CNR) of 42 dB. The feasibility of the scheme is also discussed from the viewpoints of connector reflectivity and fiber-dispersion.

Influence of reflected light on erbium-doped fiber amplifiers for optical AM video signal transmission systems

Investigates experimentally the influence of reflected light on an erbium-doped fiber amplifier for use in optical AM frequency-division multiplexing (FDM) video distribution systems when reflection points exist before and after the amplifier. It is found that amplifier distortion is not affected by reflected light but that the signal gain and the noise figure of the fiber amplifier degrade with increased reflectivity. Gain was decreased by 3 dB when reflectivity after the amplifier was -12 dB. It was theoretically and experimentally clarified that the noise figure degradation was related to the internal reflection of the erbium-doped fiber, in addition to the reflection before and after the fiber amplifier. This internal reflection is caused by input signal light scattered within the erbium-doped fiber. >

Using equalizers to offset the deterioration in SCM video transmission due to fiber dispersion and EDFA gain tilt

The carrier-to-noise ratio (CNR) and distortion of a 1.55 mu m amplitude-modulated subcarrier-multiplexed (AM-SCM) video transmission system are worsened by the dispersion of the 1.3 mu m zero-dispersion fiber. Distortion is also increased by the EDFA gain tilt. Both problems are shown to be corrected by the use of dispersion equalizers and gain tilt equalizers. The application of the equalizers to SCM video transmission systems is proposed. >

Super-wide-band optical FM modulation scheme and its application to multichannel AM video transmission systems

A novel super-wide-band optical FM modulation scheme employing an optical heterodyne detection technique is proposed and demonstrated. Experimental results show that by applying this scheme to 40-channel AM video transmission, the power budget is expanded by approximately 10 dB at a CNR of 42 dB.

All-fiber video distribution (AFVD) systems using SCM and EDFA techniques

this paper describe the design and performance of all-fiber video distribution (AFVD) systems based on AM/FM FDM subcarrier multiplexing (SCM) and erbium-doped fiber amplifiers (EDFAs). The impact of applying EDFAs to SCM analog video distribution systems is investigated. AM/FM hybrid systems, which can simultaneously distribute 11 AM TV channels and 50 FM TV channels are proposed and discussed. Four-stage amplifier-branch transmission experiments are introduced. The construction and performance of a newly designed 50-channel FM tuner are also presented.

Fully engineered multi-channel FM-SCM video distribution systems

This paper reports the design and performance of a multi-channel FM-SCM video distribution system that can be placed into practical use. Fifty FM video channels can be delivered to more than 10 000 customers through three-cascaded erbium-doped fiber amplifiers, and wideband/low-noise analog SCM links. As the outdoor plant is completely passive, reliability and easy maintenance can be expected. An evaluation of fabricated equipment shows good transmission quality and stable operation. >

Signal Crosstalk due to Fiber Nonlinearity in Wavelength Multiplexed SCM-AM-TV Transmission Systems

Recent experiments have examined the transmission of analog multi-channel AM-SCM video signals over conventional, 1.3μm optimized, fiber by using praseodymium-doped fluoride fiber amplifiers (PDFFAs) [1]-[3]. However, the simultaneous amplification and transmission of wavelength multiplexed AM-SCM video signals by using PDFFAs has not yet been demonstrated.

Intermodulation distortion in 48 TV channel FM-FDM optical transmission

The effect of dispersive fibers on multichannel FM video transmission characteristics is experimentally investigated. A directly modulated 1.5 mu m distributed feedback laser diode (DFB-LD) and a LiNbO/sub 3/ external modulator with a continuous-wave (CW) 1.55 mu m DFB-LD are used as optical signal sources. When the 1.3 mu m single-mode fiber (SMF) is used, directly modulated DFB-LDs suffer from second-and third-order intermodulation distortion (IMD). The external modulator realizes good transmission characteristics irrespective of the fibers dispersion value. This means that external modulators can realize multichannel FM television signal transmission systems that use the standard 1.3 mu m SMF already installed in fiber optic subscriber loops.<<ETX>>

Polarization dependent distortion in AM-SCM video transmission systems

The second-order intermodulation distortion product, namely composite second-order (CSO) distortion, of an AM-SCM video transmission system can be caused by the optical isolators, cascaded fiber amplifiers, or the fiber transmission cable employed. Moreover, the absolute distortion value depends on the polarization angle of light input to the optical isolators, cascaded fiber amplifiers, and fiber transmission line. The degraded distortion values are measured and their mechanisms are clarified. >