Abstract

In free space optical data transmission systems illumination of the receiver antenna by background radiation will decrease the signal to noise ratio. We derive expressions for that degradation both for direct and for heterodyne/homodyne receivers. Examples are given for cases where the sun, the moon, the earth, and Venus illuminate earth orbiting receivers operating at wavelengths of 0.85 μm, 1.3 μm, and 10.6 μm. Direct detection receivers will typically suffer a degradation of between 5 and 15 dB at λ = 0.85 μm and λ = 1.3 μm when illuminated by the sun. Heterodyne/homodyne receivers at 10.6 μm degrade more with sun radiation (typically 4 dB) than at the smaller wavelengths (≈0.3 dB). The moon, earth, and Venus cause negligible reduction of signal to noise ratio.

© 1989 Optical Society of America

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References

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  1. K. Bhasin, Ed., Optical Technologies for Communication Satellite Applications, Proc. Soc. Photo-Opt. Instrum. Eng.616, (1986).
  2. K. Bhasin, G. A. Koepf, Eds., Optical Technologies for Space Communication Systems, Proc. Soc. Photo-Opt. Instrum. Eng.756, (1987).
  3. H. Lutz, G. Otrio, Eds., Optical Systems for Space Applications, Proc. Soc. Photo-Opt. Instrum. Eng.810, (1987).
  4. G. A. Koepf, D. L. Begley, Eds., Free-Space Laser Communication Technologies, Proc. Soc. Photo-Opt. Instrum. Eng.885, (1988).
  5. A preliminary account on that subject was presented by W. R. Leeb at the conference SPIE’88, Los Angeles, 1988, and was published in Ref. 4, p. 85–92.
  6. W. B. Davenport, W. L. Root, Random Signals and Noise, Chap. 12 (McGraw-Hill, New York, 1958).
  7. M. Schwarz, Information Transmission, Modulation, and Noise, Chap. 5–11 (McGraw-Hill, New York, 1985).
  8. R. H. Kingston, Detection of Optical and Infrared Radiation (Springer-Verlag, New York, 1978), Chap. 7.1.
  9. W. K. Pratt, Laser Communication Systems (Wiley, New York, 1969), Chap. 6.
  10. R. M. Gagliardi, S. Karp, Optical Communications (Wiley, New York, 1976).
  11. R. C. Ramsey, “Spectral Irradiance from Stars and Planets, Above the Atmosphere, from 0.1 to 100.0 Microns,” Appl. Opt. 1, 465–471 (1962).
    [CrossRef]

1962

Davenport, W. B.

W. B. Davenport, W. L. Root, Random Signals and Noise, Chap. 12 (McGraw-Hill, New York, 1958).

Gagliardi, R. M.

R. M. Gagliardi, S. Karp, Optical Communications (Wiley, New York, 1976).

Karp, S.

R. M. Gagliardi, S. Karp, Optical Communications (Wiley, New York, 1976).

Kingston, R. H.

R. H. Kingston, Detection of Optical and Infrared Radiation (Springer-Verlag, New York, 1978), Chap. 7.1.

Pratt, W. K.

W. K. Pratt, Laser Communication Systems (Wiley, New York, 1969), Chap. 6.

Ramsey, R. C.

Root, W. L.

W. B. Davenport, W. L. Root, Random Signals and Noise, Chap. 12 (McGraw-Hill, New York, 1958).

Schwarz, M.

M. Schwarz, Information Transmission, Modulation, and Noise, Chap. 5–11 (McGraw-Hill, New York, 1985).

Appl. Opt.

Other

K. Bhasin, Ed., Optical Technologies for Communication Satellite Applications, Proc. Soc. Photo-Opt. Instrum. Eng.616, (1986).

K. Bhasin, G. A. Koepf, Eds., Optical Technologies for Space Communication Systems, Proc. Soc. Photo-Opt. Instrum. Eng.756, (1987).

H. Lutz, G. Otrio, Eds., Optical Systems for Space Applications, Proc. Soc. Photo-Opt. Instrum. Eng.810, (1987).

G. A. Koepf, D. L. Begley, Eds., Free-Space Laser Communication Technologies, Proc. Soc. Photo-Opt. Instrum. Eng.885, (1988).

A preliminary account on that subject was presented by W. R. Leeb at the conference SPIE’88, Los Angeles, 1988, and was published in Ref. 4, p. 85–92.

W. B. Davenport, W. L. Root, Random Signals and Noise, Chap. 12 (McGraw-Hill, New York, 1958).

M. Schwarz, Information Transmission, Modulation, and Noise, Chap. 5–11 (McGraw-Hill, New York, 1985).

R. H. Kingston, Detection of Optical and Infrared Radiation (Springer-Verlag, New York, 1978), Chap. 7.1.

W. K. Pratt, Laser Communication Systems (Wiley, New York, 1969), Chap. 6.

R. M. Gagliardi, S. Karp, Optical Communications (Wiley, New York, 1976).

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Figures (5)

Fig. 1
Fig. 1

Block diagram of the photomixing process of a sinusoidal signal (field e I , frequency f L , power P I ) and white noise (field e N , spectral power density N) at a photodetector with optical filter of bandwidth b(Δλ).

Fig. 2
Fig. 2

Spectra arising in the photomixing process modeled in Fig. 1. a) Optical spectrum and diode input. b) Electrical output spectrum.

Fig. 3
Fig. 3

Degradation of direct detection signal to noise ratio due to solar radiation as a function of input power P S normalized to photon energy hf, i.e., as a function of the rate of arriving photons during a mark. The lower abscissa axis gives the data rate R S in case the indicated number of photons ( n ¯ ) arrive per bit. The parameter β characterizes the closeness of the receiver’s sensitivity to the quantum limit in case of zero background. The ratio of actual to diffraction limited field of view is γ = Ω FV DL = 3, further λ = 0.85 μm, Δλ = 5 nm, η = 0.9, F = 4.

Fig. 4
Fig. 4

As Fig. 3, but for λ = 1.3 μm, Δλ = 8 nm, η = 0.8, F = 6.

Fig. 5
Fig. 5

Degradation of heterodyne signal to noise ratio due to solar radiation as a function of receiver’s deviation β from shot-noise limited operation under zero background. Wavelengths and detector quantum efficiencies are indicated. Further ζ O = 0.8.

Tables (3)

Tables Icon

Table I Spectrum of Diode Output

Tables Icon

Table II Spectral Power Density per Mode, N′, (in W Hz−1) Produced by Various Celestial Bodies at Selected Wavelengths a

Tables Icon

Table III Effective Temperature, Peak Spectral Irradiance, and Spectral Radiance (Single State of Polarization) due to Sun Reflectance and Self-Emission9,11, a

Equations (46)

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i [ e I ( t ) + e N ( t ) ] 2 ¯ R .
R = η e h f ,
i S N 2 ¯ = 2 e B R ( P I + b N ) ,
SNR D = ( R P S M ) 2 M 2 F 2 e B [ R ( P S + b N ) + I D ] + M 2 2 B R 2 N ( 2 P S + b N ) / m + 4 k T C B / R L ,
N = N / m ,
m = Ω F V / Ω D L .
m = Ω S / Ω D L .
γ = Ω F V / Ω D L ,
= Ω F V / Ω S ,
m = γ ( if 1 )
m = γ / ( if 1 ) .
β = SNR D , qu . lim . SNR D ( N = 0 ) ,
SNR D , qu . lim . = η P S 2 h f B .
β = 10 log β .
SNR D = R P S / ( 2 e B ) β + N b F P S + N R e m ( 2 + N b P S ) .
deg D = 10 log [ SNR D ( N = 0 ) / SNR D ] ,
deg D = 10 log { 1 + 1 β [ m N b P S ( F + N η h f ) + 2 N η h f ] } ,
P S = 2 h f n ¯ R S .
b = Δ λ c / λ 2 .
deg D = 10 log { 1 + 1 β [ h f m Δ λ c λ 2 P S E ( F + η E ) + 2 η E ] } ,
E = exp ( h c λ k T ) 1 ,
deg D = 10 log { 1 + 1 β [ m N Δ λ 2 h λ n ¯ R S ( F + N η λ h c ) + 2 N η λ h c ] } .
m = Ω S / Ω D L = Ω S A / λ 2 ,
Ω D L = λ 2 / A ,
SNR H = 2 R 2 P O P S ζ O 2 e B [ R ( P O + b N ) + I D ] + 2 B R 2 N ( 2 P O ζ O + b N ) / m + 4 k T C B / R L .
SNR H , P O = η P S ζ O / ( h f B ) 1 + 2 η N ζ O / ( h f m ) .
SNR H , qu . lim . = η P S ζ O / h f B .
β = 1 + I D / R P O + 2 k T C / ( e R P O R L ) ,
SNR H = R P S ζ O e B ( β + b N P O + 2 N R e m + R N 2 b e P O m ) .
deg H = 10 log [ 1 + 1 β m N b P O ( 1 + η N h f ) + 2 N η β h f ζ O ] .
deg H = 10 log [ 1 + 2 N η β h f ζ O ] .
deg H = 10 log ( 1 + 2 η ζ O / { β [ exp ( h c / k T λ ) 1 ] } ) ,
N = N ( f ) λ 2 γ ( if = Ω F V / Ω S 1 ) ,
N = N ( f ) A Ω S ( if 1 ) .
γ = Ω F V Ω D L ( γ 1 ) ,
N = N / m ,
N = N ( f ) λ 2 .
N ( f ) = h f 3 c 2 [ exp ( h f / k T ) 1 ] 1 ,
N = h f [ exp ( h f / k T ) 1 ] 1 ,
H ( f ) = H ( λ ) λ 2 / c ,
N = H ( f ) A ( if 1 ) ,
N = H ( f ) A ( if 1 ) .
N = H ( λ ) λ 4 / ( c Ω S ) .
H ( λ ) = H ( λ ) peak 2 . 93 × 10 11 m 5 K 5 ( λ T eff ) 5 [ exp ( h c / λ k T eff ) 1 ] .
N ( λ ) = N ( λ ) peak 2 . 93 × 10 11 m 5 K 5 ( λ T eff ) 5 [ exp ( h c / λ k T eff ) 1 ] .
N ( f ) = N ( λ ) λ 2 / c ,

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