In Section I it is demonstrated that the amplitude of the light deflected 01

The transmission line matrix formalism so useful for describing the transfer properties of microwave networks is extended to the electromagnetic fields associated with optical masers. The spontaneous emission noise of the optical maser is examined and shown to be amenable to a thermal description. Taking the point of view, well accepted at microwave frequencies, that a weakly nonlinear oscillator is a saturated amplifier of noise, the power and linewidth of the noise radiation emitted by the optical maser is calculated using the transmission line formalism. The significant parameters for any optical maser are shown to be the frequency, the single‐pass gain of the maser medium, the effective mirror reflectivity and the population ratio. The pre‐oscillation characteristics of the maser are examined and the reason for the extremely sharp oscillation threshold of the gas masers is discussed. Some observations concerning semiconductor optical masers are also made.

The Fabry‐Perot modulator, consisting of Fabry‐Perot etalon plates separated by an electrooptic material such as KDP, is analyzed in detail. Time‐dependent perturbation theory is used to describe the coupling of the axial modes by spatial and time varying perturbations in the dielectric constant. The perturbations are produced by the applied microwave modulating field. It is shown that the correct choice of the spatial variation of the microwave modulating field is essential to achieve efficient modulation and the choice is equivalent to matching the phase velocities of the microwaves and the light. Power requirements, heating, and bandwidth are discussed and a comparison is made to the traveling‐wave modulator described by Kaminow. Calculations indicate that bandwidths of several hundred megacycles, centered at any microwave frequency, can be obtained with the expenditure of several watts of modulating power.

A new reliability assurance philosophy is described that represents the Bell System approach to solving the difficult problem of providing new device technology for early system deployment with well characterized and desirable reliability characteristics. This philosophy is especially important for high reliability systems such as satellites and submarine cables.It is based on the use of very high stresses, both thermal and nonthermal, to eliminate failure modes which are only weakly temperature activated, and to stabilize degradation rates. The technique is called "purging." HE USE of new technology devices in a system under de-T v e l o p m e n t carries with it the potential for significant improvements in the performance, cost, and market appeal of the new system. However; the new technology devices imply risks for the system designer. Short schedules imply uncertainty in availability and cost, and performance parameters may not be specified precisely. The area of greatest concern and risk frequently centers on device reliability. With the device design not frozen, with manufacturing processes not fully specified, and with manufacturing facilities still under construction, the device developer is required to complete a qualification program that yields responsible estimates of the device reliability and quality.For many systems and related products, the satisfactory reliability and assurance thereof is not available in time for early deployment, The development-manufacturing team recognizes the necessary cost of low assembly yield and field replacement, hopes it won't be excessive and goes on to meet shipment schedules without full reliability assurance. With hard work, a developing data base, and device design and process iteration, the reliability requirements are eventually met. However, for some systems, for example, undersea cables and satellites, such a strategy is not feasible. These systems, because field replacement is not possible or excessively expensive, must have adequate information to make reliability predictions for new technology devices before deployment, despite exceptionally tight schedules.The challenge of implementing a new digital submarine cable system in 1988 has focused attention on reliability issues for new devices, such as optical sources, detectors, etc. Certain of these devices will not have seen field use in other less critical systems before completing design of the submarine cable system. Out of this focus has come a philosophy of reliability qualification that has been exceptionally successful and has implications for all new technology semiconductor devices.

A review of the principles of acoustooptical devices is given. Some very simple momentum conservation considerations indicate the optimum relationship between the optical and acoustic beam dimensions for various functions such as scanning or modulation. A calculation for the usual type of acoustic amplitude modulation is described, and serves as an example of the type of detailed considerations that are necessary and possible, as well as a verification of the validity of the simple momentum considerations. It is shown that the product of the fraction of the light that may be scattered and the bandwidth for Bragg scattering equals a materials constant times the acoustic power. This relationship is shown to be valid even to the extent of numerical constants for several configurations allowing a trade-off between these parameters. Thus, the required modulation power for any level of device performance is easily determined. The details of acoustic deflection under conditions of acoustic beam focusing or scanning are also given.