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Exhibit 10.50 ADDENDUM
TO
STOCK OPTION AGREEMENT The following provisions are hereby incorporated into, and are hereby made a part of, that
certain Stock Option Agreement (the Option Agreement) by and between Advanced Fibre
Communications, Inc. (the Corporation) and [optionee name] (Optionee) evidencing the stock
option (the Option) granted this day to Optionee under the terms of the Corporations 1996 Stock
Incentive Plan, and such provisions shall be effective immediately. All capitalized terms in this Addendum, to the extent not otherwise defined herein, shall have
the meanings assigned to them in the Option Agreement. INVOLUNTARY TERMINATION FOLLOWING
CORPORATE TRANSACTION/CHANGE IN CONTROL 1. To the extent the Option is, in connection with a Corporate Transaction, either to be
assumed by the successor entity (or parent company) or to be replaced with a cash incentive program
in accordance with Paragraph 6 of the Option Agreement, the Option shall not vest on an accelerated
basis upon the occurrence of that Corporate Transaction, and the Option shall accordingly continue,
over Optionees period of Service after the Corporate Transaction, to become exercisable for the
Option Shares in one or more installments in accordance with the provisions of the Option
Agreement. However, immediately upon an Involuntary Termination of Optionees Service within
eighteen (18) months following such Corporate Transaction, the Option (or any replacement grant),
to the extent outstanding at the time but not otherwise fully exercisable, shall automatically vest
and become immediately exercisable for all the Option Shares at the time subject to the Option and
may be exercised for any or all of those Option Shares as fully vested shares. 2. The Option shall not vest on an accelerated basis upon the occurrence of a Change in
Control, and the Option shall, over Optionees period of Service following such Change in Control,
continue to become exercisable for the Option Shares in accordance with the provisions of the
Option Agreement. However, immediately upon an Involuntary Termination of Optionees Service
within eighteen (18) months following the Change in Control, the Option, to the extent outstanding
at the time but not otherwise fully exercisable, shall automatically vest and become immediately
exercisable for all the Option Shares at the time subject to the Option and may be exercised for
any or all of those Option Shares as fully vested shares. 3. The Option as accelerated under Paragraphs 1 or 2 shall remain so exercisable until the
earlier of (i) the Expiration Date or (ii) the expiration of the one (1)-year period
measured from the date of the Optionees Involuntary Termination.




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4. For purposes of this Addendum the following definitions shall be in effect: (i) An Involuntary Terminationshall mean the termination of Optionees Service
by reason of: (A) Optionees involuntary dismissal or discharge by the Corporation
for reasons other than Misconduct, or (B) Optionees voluntary resignation following (A) a change in
Optionees position with the Corporation (or Parent or Subsidiary employing
Optionee) which materially reduces Optionees duties and responsibilities,
(B) a reduction in Optionees level of compensation (including base salary,
fringe benefits and target bonus under any performance based bonus or
incentive programs) by more than fifteen percent (15%) or (C) a relocation
of Optionees place of employment by more than fifty (50) miles, provided
and only if such change, reduction or relocation is effected by the
Corporation without Optionees consent. (ii) A Change in Controlshall be deemed to occur in the event of a change in
ownership or control of the Corporation effected through either of the following
transactions: (A) the acquisition, directly or indirectly, by any person or related
group of persons (other than the Corporation or a person that directly or
indirectly controls, or is controlled by, or is under common control with,
the Corporation) of beneficial ownership (within the meaning of Rule 13d-3
of the Securities Exchange Act of 1934, as amended) of securities possessing
more than fifty percent (50%) of the total combined voting power of the
Corporations outstanding securities pursuant to a tender or exchange offer
made directly to the Corporations stockholders which the Board does not
recommend such stockholders to accept, or (B) a change in the composition of the Board over a period of
thirty-six (36) consecutive months or less such that a majority of the Board
members ceases, by reason of one or more contested elections for Board
membership, to be comprised of individuals who either (i) have been Board
members continuously since the beginning of such period or (ii) have been
elected or nominated for election as Board members during such period by at
least a majority of the Board members described in clause (i) who were still
in office at the time such election or nomination was approved by the Board. 2.




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5. The provisions of Paragraph 3 of this Addendum shall govern the period for which the Option
is to remain exercisable following the Involuntary Termination of Optionees Service within
eighteen (18) months after the Corporate Transaction or Change in Control and shall supersede any
provisions to the contrary in Paragraph 5 of the Option Agreement. IN WITNESS WHEREOF,Advanced Fibre Communications, Inc. has caused this Addendum to be
executed by its duly-authorized officer as of the Effective Date specified below. ADVANCED FIBRE COMMUNICATIONS, INC.By:Title: EFFECTIVE DATE:__________________ 3.