The 1995 Stock Plan provides for the grant of incentive stock options, non-statutory stock options and restricted stock units (“RSUs”). Incentive stock options may be granted only to employees. All other awards may be granted to employees and non-employees. Under the terms of the 1995 Stock Plan, no incentive stock option or non-statutory stock option may be granted in the ordinary course of business with a per share exercise price that is less than 100% of the fair value of the Company’s common stock on the date of grant. RSUs have no exercise price. Both options and RSUs vest over a period of time as determined by the Company’s Board of Directors (the “Board”), generally two to four years, and options expire seven years from the date of grant. Some of the RSUs granted by the Company have performance-based vesting terms, where vesting is dependent on achievement of certain financial and non-financial operating goals of the Company (performance-based RSUs, or “PRSUs”), or where vesting is dependent on performance of the Company’s total shareholder return (“TSR”) relative to the TSR of the Nasdaq Telecommunication Index (market-based RSUs, or “MRSUs”). The fair value of PRSUs is estimated on the date of grant based on the market value of our common stock. If the performance goals are not met as of the end of the performance period, no compensation expense is recognized and any previously recognized compensation expense is reversed. The expected cost is based on the portion of the awards that is probable to vest and is reflected over the service period. The fair value of MRSUs subject to targeted levels of relative TSR is estimated on the date of grant using a Monte Carlo simulation model. Compensation expense is recognized based upon the assumption of 100% achievement of the TSR goal and will not be reversed even if the threshold level of TSR is never achieved and is reflected over the service period. The 1995 Stock Plan was replaced by the 2025 Stock Plan in June 2025.

The 2002 Director Plan provides for the grant of non-statutory stock options and RSUs to non-employee directors of the Company. Under the terms of the 2002 Director Plan, no non-statutory stock option may be granted with a per share exercise price that is less than 100% of the fair value of the Company’s common stock on the date of grant. RSUs have no exercise price. Both options and RSUs vest over a period of time as determined by the Board, generally one year for RSUs and three years for options, and options expire seven years from the date of grant. The 1995 Stock Plan was replaced by the 2025 Stock Plan in June 2025.

In June 2025, the Company’s stockholders approved the 2025 Equity Incentive Plan (the “2025 Stock Plan”) to replace the 1995 Stock Plan and 2002 Director Plan. As of December 31, 2025, an aggregate of 6,862,417 shares of common stock were reserved for issuance under the 2025 Stock Plan, of which 5,157,932 shares remained available for future grants. During the fiscal year 2025, the Company granted 47,048 and 188,190 shares of PRSUs and MRSUs, respectively, under the 1995 Stock Plan.

The 2002 Employee Stock Purchase Plan (“ESPP”) provides for the issuance of share purchase rights to employees of the Company. The ESPP is intended to qualify as an “employee stock purchase plan” under Section 423 of the Internal Revenue Code. The ESPP enables employees to purchase shares at 85% of the fair market value of the Common Stock at the beginning or end of the offering period, whichever is lower. Offering periods generally begin on the first trading day on or after January 1 and July 1 of each year. Employees may participate through payroll deductions of 1% to 10% of their earnings. In the event that there are insufficient shares in the plan to fully fund the issuance, the available shares will be allocated across all participants based on their contributions relative to the total contributions received for the offering period. In June 2025, the Company’s stockholders approved an amendment to the ESPP Plan at the 2025 Annual Meeting to increase the number of shares of common stock reserved for issuance thereunder by 500,000 shares. As of December 31, 2025, 408,348 shares were reserved for future purchases by eligible employees. Under the ESPP, 653,580, 622,004 and 733,030 shares were issued during fiscal 2025, 2024 and 2023, respectively, representing $6.0 million, $6.6 million and $6.6 million in contributions.

All stock options were fully vested and exercised as of December 31, 2023. No stock options were granted in 2024 and 2025.


(in thousands, except per share amounts)	Number of Shares		Weighted Average Grant-Date Fair Value Per Share
Balance at December 31, 2024		3,447	$	12.95
Granted		3,212		9.42
Vested and issued		(2,354)		12.68
Forfeited		(170)		12.78
Balance at December 31, 2025		4,135	$	10.36

The fair value of RSUs vested and issued during the years ended December 31, 2025, 2024 and 2023 was $29.9 million, $25.6 million and $22.5 million, respectively.

The following table sets forth the detailed allocation of the share-based compensation expense which was included in the Company’s Consolidated Statements of Operations:


		Year Ended December 31,
(in thousands)	2025		2024		2023
Share-based compensation expense included in:
Cost of revenue	$	963	$	506	$	963
Research and development expense		4,751		4,609		3,616
Selling, general and administrative expense		15,929		14,211		11,841
Total	$	21,643	$	19,326	$	16,420

Share-based compensation expense by type of award:
RSUs	$	17,416	$	16,344	$	13,308
PRSUs		39		200		—
MRSUs		3,140		1,646		1,800
Employee stock purchase rights under ESPP		1,048		1,136		1,312
Total	$	21,643	$	19,326	$	16,420

As of December 31, 2025, total unrecognized share-based compensation cost related to unvested RSUs was $21.1 million and is expected to be recognized over a weighted-average period of approximately 1.5 years.

The Company estimates the fair value of stock purchase rights under the ESPP using a Black-Scholes option valuation model. The value of the stock purchase rights under the ESPP consists of: (1) the 15% discount on the purchase of the stock; (2) 85% of the fair value of the call option; and (3) 15% of the fair value of the put option. The call option and put option were valued using the Black-Scholes option pricing model. At the date of grant, the Company estimated the fair value of each stock purchase right granted under the ESPP using the following weighted average assumptions:


	Year Ended December 31,
	2025		2024		2023
Expected term (in years)		0.50		0.50		0.50
Volatility		41%		50%		46%
Risk-free interest rate		3.9%		5.3%		5.2%
Expected dividends		0.0%		0.0%		0.0%

The expected term of the stock purchase right under ESPP represents the period of time from the beginning of the offering period to the purchase date. The Company uses its historical volatility for a period equivalent to the expected term to estimate the expected volatility. The risk-free interest rate that the Company uses in the Black-Scholes option valuation model is based on U.S. Treasury zero-coupon issues with remaining terms similar to the expected term. The Company has not paid and does not plan to pay any cash dividends in the foreseeable future.

The estimated weighted-average fair value per share of stock purchase rights under the ESPP, granted for the years ended December 31, 2025, 2024 and 2023 was $3.46, $3.76 and $4.23, respectively.