US 4288785

Patent Overview: US4288785A

Title: Light intensity modulator with digital control and a digital-analog converter comprising such a modulator

Patent Number: US4288785A

Original Assignee: Thomson CSF SA (current assignee listed as Thales SA)

Inventor(s): Michel Papuchon, Claude Puech, Jean C. Anne

Key Dates:

• Prior art date / Priority date: 1979-05-23
• Filing date: 1980-05-20
• Publication (grant) date: 1981-09-08
• Anticipated expiration: 2000-05-20
• Legal status: Expired – Lifetime

Purpose:
The invention relates to a digitally controlled light intensity modulator constructed with integrated optics, aiming to use the same optical structure to construct a multiple-control-signal modulator where the signals are digital (two voltage states). It is intended for telecommunication and data processing applications and seeks low control voltages, preferably of the same order as TTL logic voltages (0–5 volts).

Plain-Language Scope:
The modulator builds on a known two-arm waveguide interferometer (e.g., monomode guides formed on an electro-optical substrate such as lithium niobate). By positioning electrodes and orienting the substrate crystal appropriately, electric fields act on the propagation speeds of waves in the arm portions opposite the electrodes, with negligible interaction between different sets of electrodes. Weighted control bits are achieved either by electrode sets of different lengths in a geometric progression conforming to successive powers of 2, or by electrode sets of equal length with voltage dividers whose ratios conform to successive powers of 2. Zero adjustment is possible via polarizing electrodes with an adjustable voltage. A digital-analog converter comprising such a modulator is also described.

Classification: G02F1/225 (interference in an optical waveguide structure); G02F7/00 (optical analogue/digital converters).

Source: https://patents.google.com/patent/[US4288785](/patent/US4288785)/en

What the excerpt does not establish:
The excerpt contains figures (1–9) referenced but not fully reproduced, and text is truncated after the discussion of electrode E_M overlapping guide 2. It does not provide the complete claims, full description, or exact wording of the digital-analog converter implementation. No litigation, ownership-transfer, validity, or prior-art information is included or assessed.