Abstract

A balanced optical discriminator for detection of angle modulation on a light beam is discussed. The device is similar, in principle, though different in form, to bridge-type microwave discriminators and optical birefringent crystal discriminators. An angle-modulated system at optical frequencies, employing a balanced discriminator, has advantages over intensity modulated systems which are familiar at radio frequencies. In addition, an angle modulated system is not as sensitive to strains, due to heating or crystal growth, in the modulating medium or to inhomogeneities in the transmission medium.

© 1964 Optical Society of America

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References

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  1. W. W. Rigrod, I. P. Kaminow, Proc. IEEE 51, 137 (1963); C. J. Peters, ibid. 51, 147 (1963).
    [CrossRef]
  2. I. P. Kaminow, Appl. Opt. 3, 511 (1964); S. E. Harris, A. E. Siegman, B. J. McMurty, in Optical Masers (Wiley, New York, 1963), M. DiDomenico, L. K. Anderson, Bell Syst. Tech. J. 42, 2621 (1963).
    [CrossRef]
  3. C. L. Ruthroff, “Microwave-to-Baseband Discriminator”, unpublished memorandum (1954); R. V. Pound in Techniques of Microwave Measurements, MIT Radiation Lab. Series, Vol. 11, C. G. Montgomery, ed. (McGraw-Hill, New York, 1947); R. J. Mohr, IRE Trans. MTT-11, 263 (1963).
    [CrossRef]
  4. S. E. Harris, Appl. Phys. Letters 2, 47 (1963).
    [CrossRef]

1964 (1)

1963 (2)

S. E. Harris, Appl. Phys. Letters 2, 47 (1963).
[CrossRef]

W. W. Rigrod, I. P. Kaminow, Proc. IEEE 51, 137 (1963); C. J. Peters, ibid. 51, 147 (1963).
[CrossRef]

Harris, S. E.

S. E. Harris, Appl. Phys. Letters 2, 47 (1963).
[CrossRef]

Kaminow, I. P.

Rigrod, W. W.

W. W. Rigrod, I. P. Kaminow, Proc. IEEE 51, 137 (1963); C. J. Peters, ibid. 51, 147 (1963).
[CrossRef]

Ruthroff, C. L.

C. L. Ruthroff, “Microwave-to-Baseband Discriminator”, unpublished memorandum (1954); R. V. Pound in Techniques of Microwave Measurements, MIT Radiation Lab. Series, Vol. 11, C. G. Montgomery, ed. (McGraw-Hill, New York, 1947); R. J. Mohr, IRE Trans. MTT-11, 263 (1963).
[CrossRef]

Appl. Opt. (1)

Appl. Phys. Letters (1)

S. E. Harris, Appl. Phys. Letters 2, 47 (1963).
[CrossRef]

Proc. IEEE (1)

W. W. Rigrod, I. P. Kaminow, Proc. IEEE 51, 137 (1963); C. J. Peters, ibid. 51, 147 (1963).
[CrossRef]

Other (1)

C. L. Ruthroff, “Microwave-to-Baseband Discriminator”, unpublished memorandum (1954); R. V. Pound in Techniques of Microwave Measurements, MIT Radiation Lab. Series, Vol. 11, C. G. Montgomery, ed. (McGraw-Hill, New York, 1947); R. J. Mohr, IRE Trans. MTT-11, 263 (1963).
[CrossRef]

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Figures (4)

Fig. 1
Fig. 1

Optical discriminator.

Fig. 2
Fig. 2

(a). Photocurrent in unbalanced discriminator. (b) Photocurrent in balanced discriminator. Ω0 is the unmodulated carrier frequency and 2ΔΩ the bandwidth.

Fig. 3
Fig. 3

Simplified optical discriminator.

Fig. 4
Fig. 4

Balanced birefringent crystal discriminator.

Equations (20)

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τ = ( L a + L b ) / 2 c , τ = ( L a L b ) / 2 c , t = t τ ,
E in = A cos ( Ω t + φ ) ,
E 1 = A 2 { cos [ Ω ( t τ ) + 2 θ T + φ ] + cos [ Ω ( t + τ ) + 2 θ R + φ ] } , E 2 = A 2 { cos [ Ω ( t τ ) + θ R + θ T + φ ] + cos [ Ω ( t + τ ) + θ R + θ T + φ ] } ,
I 1 = A 2 4 [ 1 + cos 2 ( θ R θ T ) ] I 2 = A 2 2 = I in .
θ R = π 2 and θ T = 0 ,
E 1 = A sin Ω τ sin ( Ω t + φ ) , E 2 = A cos Ω τ sin ( Ω t + φ ) ,
I 1 = A 2 2 sin 2 Ω τ , I 2 = A 2 2 cos 2 Ω τ .
Ω 0 τ = π 4 + n π ,
Δ Ω τ < π 4 ,
i = i 2 i 1 = K A 2 2 cos 2 Ω τ .
E in = j A j cos ( Ω j t + φ j ) ,
E 1 = j A j sin Ω j τ sin ( Ω j t + φ j ) , E 2 = j A j cos Ω j τ sin ( Ω j t + φ j ) .
i = ( K / 2 ) j k A j A k cos ( Ω j + Ω k ) τ cos [ ( Ω j Ω k ) t + ( φ j φ k ) ] .
A 0 A k A j A k , j 0 ,
Δ Ω τ 1 ,
i K A 0 τ k ( Ω k Ω 0 ) A k cos [ ( Ω k Ω 0 ) t + ( φ k φ 0 ) ] ,
| L a L b | θ 2 λ 0 / 2 ,
| L a L b | θ d ,
λ m λ 0 16 d 2 1 ,
τ = L 2 c ( n a n b ) ,

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